Biology 3.5 3.4 and 10.2
What is the cause of sickle-cell anemia? A. A change to the base sequence of a hemoglobin gene B. Mosquitoes acting as the vector for malaria C. Iron deficiency due to the malaria parasite D. Production of more white blood cells than red blood cells by bone marrow
A
Which of the following processes result in the production of recombinants? I. Crossing over between linked genes II. Reassortment of non-linked genes III. Mutation A. I only B. I and II only C. I and III only D. I, II and III
B
Using an example, describe polygenic inheritance.
more than one gene contribute to/control same characteristic; as number of genes increase so does possible number of phenotypes; leads to continuous variation; specific example; (eg human skin color (due to differing amounts of melanin))
Gene transfer to bacteria often involves small circles of DNA into which genes can be inserted. State the name of a small circle of DNA, used for DNA transfer, in bacteria.
plasmid
Define the term allele as used in genetics.
allele: one specific form of a gene
Explain how the recombinants are formed during meiosis.
(recombination) occurs in prophase 1 of meiosis; homologous chromosomes come together in pairs; chiasmata form between the (non-sister) chromatids; chromosomes exchange segments / crossing over takes place;
Describe the characteristics of stem cells that make them potentially useful in medicine.
(stem cells) have/retain the capacity to divide; can be used to produce cell cultures/large number of identical cells; can be used to repair/replace damaged/lost cells/tissue; (stem cells) are undifferentiated / have not yet differentiated/specialized; can differentiate/specialize in different ways / are pluripotent/totipotent; can be used to form a variety of different tissues / form organs; used in medical research; used in treatment of (named) disease;
What makes gene transfer between species possible? A. All species use the same genetic code. B. All species have the same genetic material. C. All species produce the same polypeptides. D. All species transcribe genes using plasmids.
A
A parent organism of unknown genotype is mated in a test cross. Half of the offspring have the same phenotype as the parent. What can be concluded from this result? A. The parent of unknown genotype is heterozygous. B. The parent of unknown genotype is homozygous dominant. C. The parent of unknown genotype is homozygous recessive. D. The parent of known genotype is heterozygous.
A
How is the polymerase chain reaction (PCR) used? A. To make many copies of a DNA molecule B. To cut DNA at specific sequences C. To splice fragments of DNA together into a plasmid D. To separate fragmented pieces of DNA based on their charge and size
A
In humans a V-shaped hair line is dominant to a straight hair line. A woman with a V-shaped hair line and a man with a straight hair line have children. The woman has a mother with a straight hair line. What is the proportion of children who are likely to have a V-shaped hair line? A. Half of the children B. A quarter of the children C. All of the children D. None of the children
A
Rhesus factor is an antigen present on the surface of red blood cells of Rhesus positive individuals. Rhesus positive (Rh+ ) is dominant to Rhesus negative (Rh- ). A mother with Rhesus negative blood gives birth to a baby with Rhesus positive blood and there are concerns that subsequent pregnancies will trigger an immune response. What is a possible explanation for why subsequent pregnancies could trigger an immune response? A. Exposure to the Rh+ antigen in the first pregnancy triggered the development of antibodies that could attack the blood of a future Rh+ baby. B. Exposure to the Rh+ antigen in the first pregnancy triggered the development of specific phagocytes that could attack the blood of a future Rh+ baby. C. The mother has developed passive immunity to the Rh+ factor. D. The mother's immune system has been weakened by pregnancy.
A
Sickle-cell anemia is caused by a mutation. How many changes to the amino acid sequence are caused by this mutation? A. 1 B. 2 C. 3 D. 4
A
What causes genetic variety in the formation of gametes during meiosis? A. Crossing over in prophase I and random orientation of homologous chromosomes in metaphase I B. Crossing over in metaphase I and random orientation of homologous chromosomes in metaphase II C. Linkage of genes in prophase I and crossing over in metaphase I D. Linkage of genes in metaphase I and random orientation of homologous chromosomes in metaphase II
A
What causes variation in both sexually and asexually reproducing organisms? A. Mutations B. Polygenic inheritance C. Crossing over D. Independent assortment
A
What is a definition of a clone? A. A group of cells derived from a single parent cell B. Differentiated cells that retain the capacity to divide C. A fetus developed specifically for medical use D. A group of cells that have lost the ability to differentiate
A
What is polygenic inheritance? A. A character that is controlled by two or more genes B. A character that is controlled by more than two copies of a gene C. Inheriting more than two alleles of a gene D. Inheriting a linked group of genes
A
Which of the following types of information are needed to construct a karyotype? I. Size of the chromosomes II. Gene mutations of the chromosomes III. Age of the individual A. I only B. II only C. I and II only D. I, II and III
A
Which statement about the polymerase chain reaction (PCR) is correct? A. PCR allows DNA to be cloned in a test tube and millions of copies can be made in hours. B. PCR allows the synthesis of RNA from DNA molecules. C. PCR is a natural process carried out by some viruses to amplify DNA molecules. D. PCR is a man-made technique used to identify the nucleotide sequence of DNA.
A
A colour blind man and a woman carrier for colour blindness have a son. What is the probability that their son will be colour blind? A. 25 % B. 50 % C. 75 % D. 100 %
B
A man of blood group A and a woman of blood group B have a child. If both are heterozygous for the gene, what are the chances of them having a child with blood group B? A. 0% B. 25% C. 50% D. 75%
B
Boys can inherit the recessive allele (c) that causes red-green colour blindness from their mother, not from their father. The allele for normal red and green vision is C. Which of the following genotypes are possible in men? A. c only B. C or c only C. CC or cc only D. CC, Cc or cc only
B
If a father with A-type blood and a mother with B-type blood have a child, what is the probability that the child will have O-type blood? A. 50 % chance if both parents have the recessive allele. B. 25 % chance if both parents have the recessive allele. C. 0 % chance because neither parent has the allele. D. 50 % chance if either parent has the recessive allele.
B
If a man with blood group O and a woman with blood group AB have children, which blood group(s) could the children have? A. Group O only B. Groups A and B only C. Group AB only D. Groups O, A, B and AB
B
In a cross between red haired cattle and white haired cattle the offspring produced are always a colour called roan (light red). If the roan cattle are interbred they produce white, roan and red offspring. How many alleles are controlling this character? A. 1 B. 2 C. 3 D. 4
B
In a human with type A blood, what determines the blood group? A. Sex chromosomes B. One or two alleles C. Multiple alleles D. Codominant alleles
B
In a plant, dark leaves are dominant to pale leaves and yellow seeds are dominant to white seeds. A heterozygous dark-leaved plant with yellow seeds was crossed with a pale-leaved plant with white seeds. A large number of offspring were produced. They were either dark-leaved with yellow seeds or pale-leaved with white seeds in equal number. What is the most likely cause of this pattern? A. Crossing over has occurred. B. The two genes are linked. C. The traits are polygenic. D. The genes are codominant.
B
In fruit flies (Drosophila melanogaster) grey body is dominant to black body and long wings are dominant to vestigial wings. Two flies heterozygous for both genes were crossed. What proportion of the offspring would be expected to have black bodies and long wings? A. 1/2 B. 3/16 C. 1/4 D. 1/16
B
In guinea pigs black coat colour is dominant to white. In a test cross between a black and a white guinea pig both black and white offspring were produced. What percentage of the offspring would be expected to be white? A. 75 % B. 50 % C. 33.3 % D. 25 %
B
In humans, wavy hair is dominant to straight hair and free ear lobes are dominant to fixed ear lobes. A man and a woman are heterozygous for both characteristics. What is the probability that their first child will have straight hair and fixed ear lobes? A. 0 B. 1/16 C. 3/16 D. 9/16
B
Skin colour is a trait controlled by polygenic inheritance. Which statement is correct? A. Skin colour shows discontinuous variation B. Individuals show a wide range of phenotypes for skin colour C. No two people have the same skin colour D. Children always have the same skin colour as one of their parents
B
The presence of freckles is a characteristic controlled by a dominant gene. Two parents who are heterozygous for the characteristic have three children, all of whom have freckles. Which statement is true if they have a fourth child? A. There is a 100 % chance that their next child will have freckles. B. There is a 75 % chance that their next child will have freckles. C. There is a 50 % chance that their next child will have freckles. D. The next child will have no freckles as the ratio is 3 with freckles to 1 without freckles.
B
What could be achieved by DNA profiling using gel electrophoresis? A. The chromosome number of an organism could be counted. B. It could be proven that human tissue found at the site of a crime did not come from a person suspected of having committed the crime. C. A karyotype could be produced. D. Extinct species of living organisms could be brought back to life.
B
What does the universal nature of the genetic code allow? A. Change of genetic code in the same species B. Transfer of genes between species C. Formation of clones D. Infection by bacteria
B
What happens to DNA fragments in electrophoresis? A. They move in a magnetic field and are separated according to their size. B. They move in an electric field and are separated according to their size. C. They move in a magnetic field and are separated according to their bases. D. They move in an electric field and are separated according to their bases.
B
What is a suspected heterozygous individual crossed with in a test cross? A. Homozygous dominant B. Homozygous recessive C. Heterozygous dominant D. Heterozygous recessive
B
What is amplified using the polymerase chain reaction (PCR)? A. Large amounts of RNA B. Small amounts of DNA C. Small amounts of protein D. Large amounts of polymers
B
What is produced by somatic-cell nuclear transfer? A. Adult sheep B. Cloned embryos C. Rooted stem-cuttings D. Genetically modified food
B
What was an aim of genetic modification of organisms? A. To provide stem cells from embryos for medical use B. To make crop plants resistant to herbicides C. To provide sperm cells for in vitro fertilization (IVF) D. To produce genetically identical sheep
B
Which genotypes are possible when a male with blood group AB and a female with blood group O have offspring? A. IAi only B. IAi and IBi C. IAi and ii D. IAi, IBi and ii
B
Which is a statement of Mendel's law of independent assortment? A. Allele pairs separate during gamete formation and recombine during fertilization. B. Allele pairs for different genes separate independently during gamete formation. C. Unlinked alleles are assorted with a 9 : 3 : 3 : 1 ratio in a dihybrid cross. D. Allele pairs for the same gene are assorted independently during gamete formation.
B
Which of the following genotypes is possible in the offspring of a homozygous male with blood group A and a female with blood group B? A. IAIA B. IAi C. ii D. IBi
B
Which process can be used to amplify small fragments of DNA? A. Gel electrophoresis B. Polymerase chain reaction C. DNA profiling D. Electron microscopy
B
Which structure found in eukaryotes has a single membrane? A. Nucleus B. Lysosome C. Chloroplast D. Mitochondrion
B
Why do humans inherit continuous variation with regard to height? A. The trait for tallness is dominant. B. The height phenotype is polygenic. C. This is a case of multiple alleles. D. Height in humans is polyclonal with multiple alleles.
B
A new allele that provides herbicide resistance is identified in soybean plants. The allele is dominant. Which of the following would be carried out in a herbicide-resistant plant to find out if it is homozygous or heterozygous for the gene? A. Gel electrophoresis B. Karyotyping C. Test cross D. DNA profiling
C
A small amount of a suspect's DNA is obtained from a crime scene. What techniques would be used to carry out DNA profiling? A. Gel electrophoresis and paternity testing B. Paternity testing and the polymerase chain reaction (PCR) C. Polymerase chain reaction (PCR) and gel electrophoresis D. Test crossing and pedigree analysis
C
If an organism that is homozygous recessive for a trait is crossed with a heterozygote, what is the chance of getting a homozygous recessive phenotype in the first generation? A. 0% B. 25% C. 50% D. 100%
C
In a person who is heterozygous for sickle-cell anemia, where is the mutation found? A. In every gamete produced B. Only in gametes carrying an X chromosome C. In all brain cells D. In blood plasma
C
In peas, tall is dominant to dwarf. In a cross between a dwarf plant and a heterozygous tall plant what percentage of the offspring will be dwarf? A. 0 % B. 25 % C. 50 % D. 100 %
C
Some of the ratios that Morgan investigated in genetic crosses did not correspond with expected Mendelian ratios. What was the cause? A. The genetic crosses used insects rather than plants. B. The results were counted more reliably than Mendel's. C. The genes in the genetic crosses were linked. D. Drosophila has more genes than plants.
C
What does therapeutic cloning involve? A. Developing genetically identical cultures of human cells for use in drug testing B. Helping infertile couples to conceive by injecting the father's sperm into the mother's egg C. Producing embryonic stem cells for medical use D. Replacing a mutant allele in an embryo to prevent genetic disease
C
What is a plasmid? A. Chloroplast DNA B. Mitochondrial DNA C. Small circle of DNA that can transfer genes to or from a prokaryote D. The bacterial chromosome
C
What is a plasmid? A. Chloroplast DNAB. Mitochondrial DNA C. Small circle of DNA that can transfer genes to or from a prokaryote D. The bacterial chromosome
C
What term describes the failure of sister chromatids to separate during anaphase II? A. Sex linkage B. Karyotyping C. Non-disjunction D. Semi-conservative replication
C
Which are the possible recombinants in a dihybrid test cross involving the linked genes JQ/jq? A. JQ/jq and JJ/Qq B. Jq/Qq and Qq/JJ C. Jq/jq and jQ/jq D. JQ/jq and Jq/jQ
C
Which process is used in polymerase chain reaction (PCR)? A. Transcription B. Translation C. Replication D. Mutation
C
Which technique separates proteins according to size? A. Treatment with restriction endonucleases B. PCR C. Gel electrophoresis D. DNA profiling
C
A certain breed of mouse can have fur that is either black or brown. A mouse breeder performs a test cross using a brown mouse to determine the unknown genotype of a black mouse. There are four offspring produced by the cross. What conclusions can be drawn? A. If the black mouse is homozygous, one of the four offspring must be brown. B. If the black mouse is heterozygous, three of the four offspring must be black. C. The black mouse must be homozygous if all four offspring are black. D. The black mouse must be heterozygous if any of the offspring are brown.
D
A child has blood group A. The father of the child has blood group B. What are the possible genotypes of the mother? I. IAIA II. IAIB III. IAi A. I only B. I and II only C. II and III only D. I, II and III
D
Human skin colour shows continuous variation. What does this indicate about the pattern of inheritance of human skin colour? A. It is dominant. B. It is sex-linked. C. It is recessive. D. It is polygenic.
D
In a fruit fly experiment, grey body, normal winged (homozygous dominant) fruit flies were mated with black body, short winged (homozygous recessive) fruit flies. The F1 dihybrid females were then used in a test cross. If the genes are always linked and no crossing over occurs, what would be the predicted ratio in the F2 generation? A. 9 : 3 : 3 : 1 B. 1 : 1 : 1 : 1 C. 3 : 1 D. 1 : 1
D
In a variety of tulips, V is the allele for variegated colour and C is the allele for compound flower. Which cross will give a 1:1:1:1 ratio of phenotypes in the offspring? A. VvCc × VvCc B. VVcc × vvCC C. VvCc × vvCc D. Vvcc × vvCc
D
In humans the ABO blood groups are an example of inheritance involving multiple alleles. In a family the parents have blood group A and blood group B respectively. Their first child has blood group O. What is the probability that their next child will have blood group B? A. 100 % B. 75 % C. 50 % D. 25 %
D
Laboratory analysis of DNA from a 40 000 year old woolly mammoth used the polymerase chain reaction (PCR). What role did the PCR have in the analysis? A. DNA denaturation B. DNA comparison C. DNA separation D. DNA amplification
D
Red-green colour blindness is a sex-linked condition. Which of the following always shows normal vision? A. A homozygous male B. A homozygous female C. A heterozygous male D. A heterozygous female
D
The feather colour of a certain breed of chicken is controlled by codominant alleles. A cross between a homozygous black-feathered chicken and a homozygous white-feathered chicken produces all speckled chickens. What phenotypic ratios would be expected from a cross between two speckled chickens? A. All speckled B. 1 black feathers : 1 white feathers C. Speckled, black feathers and white feathers in equal numbers D. 1 black feathers : 2 speckled feathers : 1 white feathers
D
The genetic determination of dogs' coats can be quite complex, with many different genes acting at the same time. • The dominant allele E gives brown tones. The recessive allele e results in red tones.• The colour intensity is due to another gene. The dominant allele B gives a dark colour, whereas the recessive allele b results in a light colour. What would be the genotype of a light brown dog produced from a cross between a dark brown dog and a light red dog? A. EEbb B. EeBb C. eeBb D. Eebb
D
What is the major health issue resulting from the Chernobyl nuclear accident in 1986? A. Coronary thrombosis B. Cholera C. Sex-linked diseases D. Thyroid cancer
D
What would be the expected result if a woman carrier for colour blindness and a colour blind man had many children? A. All offspring will be colour blind. B. All male offspring will be colour blind and all females normal. C. All males will be normal and all females will be colour blind. D. All females will be carriers of colour blindness or colour blind
D
When genes are transferred between species, the amino acid sequence of the polypeptide translated from them is unchanged. Why is this so? A. All organisms use ribosomes for protein synthesis. B. DNA replication is semi-conservative. C. The enzymes used are substrate specific. D. The genetic code is universal.
D
Which disease is an example of sex-linked (X-linked) inheritance? A. AIDS B. Down syndrome C. Sickle-cell anemia D. Hemophilia
D
Which enzymes are needed to produce recombinant plasmids to be used in gene transfer? A. DNA polymerase and DNA ligase B. DNA polymerase and restriction enzyme (endonuclease) C. Transcriptase and RNA polymerase D. Restriction enzyme (endonuclease) and DNA ligase
D
Which is a feature of sex-linked genes in humans? A. Males can only be heterozygous for the gene. B. Females can only be homozygous for the gene. C. Males can be either heterozygous or homozygous for the gene. D. Females can be either heterozygous or homozygous for the gene.
D
Which is a possible risk associated with a genetic modification of crops? A. Crop plants will become weaker with time. B. It can increase mutations in the organisms that consume them. C. Starch obtained from genetically modified plants will be more difficult to digest. D. Resistance to herbicide genes can be transferred to weeds.
D
Which sequence of DNA would be suitable in DNA profiling? A. ---ATTCGTGAATCAGCC-- B. ---ATTCGTGAATTTGCC-- C. ---ATTCGTGATTGCAGC-- D. ---ATTCGTGATTCGTGA--
D
Which technique causes fragments of DNA to move in an electric field? A. Polymerase chain reaction (PCR) B. Genetic modification C. Therapeutic cloning D. Gel electrophoresis
D
Discuss the relationship between one gene and one polypeptide.
DNA codes for a specific sequence of amino acids/polypeptide; the DNA code for one polypeptide is a gene; DNA is transcribed into mRNA; mRNA moves to a ribosome; where mRNA is translated into a polypeptide; originally it was thought that one gene always codes for one polypeptide; some genes do not code for a polypeptide; some genes code for transfer RNA/tRNA/ribosomal RNA/rRNA; some sections of DNA code for regulators that are not polypeptides; antibody production does not follow this pattern (of simple transcription-translation); (allow other examples) change in the gene/mutation will affect the primary structure of the polypeptide;
Discuss the benefits and possible harmful effects of altering species by one example of genetic modification.
DNA is universal (genes can be transferred among species); gene modification is the transfer of genetic material between species; named example; (e.g. glyphosate resistant crops)source of gene; (e.g. bacteria) function of gene; (e.g. resistance to herbicides) modified organisms; (e.g. soya beans) argument in favour/benefit of named example; (e.g. increase in crop yield) argument in favour/benefit of named example; (e.g. reduction in use of herbicides) argument in favour/benefit of named example; (e.g. glyphosate breaks down into naturally occurring components so glyphosate resistant crops are justified) argument against/risk of named example; (e.g. (application of) glyphosate could cause cancer in future) argument against/risk of named example; (e.g. could be transferred to wild plants) argument against/risk of named example; (e.g. genetically modified crops may cause allergies)
A small DNA sample found at a crime scene can be used in an investigation. Describe the steps taken in the processing of this small sample of DNA.
DNA samples are taken from crime scene, suspects and victims; polymerase chain reaction/PCR used to increase the amount of DNA; restriction enzymes used to cut DNA; electrophoresis involves electric field/placing sample between electrodes; used to separate DNA fragments according to size; creating DNA profiles/unique patterns of bands; comparison is made between the patterns; criminals/victims can be identified in this way; DNA is (quite) stable / DNA can be processed long after the crime;
Explain the use of karyotyping in human genetics.
Definition and construction of karyotypes: karyotype is the number and type / image of chromosomes in a cell; cells collected from chorionic villus / by amniocentesis; requires cells in metaphase / stimulate cells to divide and reach metaphase; burst cells and spread chromosomes / photo taken of chromosomes; chromosomes are arranged in pairs; according to size/structure/position of centromere/banding pattern; Uses for karyotypes: karyotypes used to identify sex/gender; male is XY and female XX; used to identify chromosome mutations/abnormal numbers/non-disjunction; Down syndrome due to extra chromosome 21 / other trisomy/aneuploidy example; used for pre-natal diagnosis of chromosome abnormalities; may lead to a decision to abort the fetus; prepare for consequences of abnormality in offspring;
Describe the causes of Down syndrome.
Down syndrome is caused by non-disjunction; occurs during meiosis; chromosome pairs fail to separate in meiosis I / chromatids in meiosis II / anaphase II; some gametes have an extra chromosome; can lead to zygotes/individuals with an extra chromosome / individual has 47 chromosomes; in Down syndrome this would be trisomy 21/extra chromosome 21; increased probability with increased age of mother/ages of parents;
Explain the process of gel electrophoresis
Gel electrophoresis is a technique used to separate DNA fragments according to their size. DNA samples are loaded into wells (indentations) at one end of a gel, and an electric current is applied to pull them through the gel. DNA fragments are negatively charged, so they move towards the positive electrode. Because all DNA fragments have the same amount of charge per mass, small fragments move through the gel faster than large ones. When a gel is stained with a DNA-binding dye, the DNA fragments can be seen as bands, each representing a group of same-sized DNA fragments.
Define linked genes.
Genes located on the same chromosomes.
List the possible genotypes for blood group B.
IBIB and IBi
Explain how evolution may happen in response to an environmental change.
a. (genetic) variation in population; b. (variation is) due to mutation / sexual reproduction; c. valid example of variation in a specific population; d. more offspring are produced than can survive / populations over-populate; e. competition / struggle for resources/survival; f. example of competition/struggle for resources; g. survival of fittest/best adapted (to the changed environment)/those with beneficial adaptations / converse; h. example of changed environment and adaptation to it; i. favourable genes/alleles passed on / best adapted reproduce (more) / converse; j. example of reproduction of individuals better adapted to changed environment; k. alleles for adaptations to the changed environment increase in the population; l. example of genes/alleles for adaptations increasing in a population; m. evolution by natural selection; n. evolution is (cumulative) change in population/species over time / change in allele frequency;
Describe the application of DNA profiling to determine paternity.
a. DNA from child, mother and possible father(s) used to establish paternity; b. (DNA profiling is done) for legal reasons / divorce / inheritance; c. (DNA profiling is done) for personal reasons / self-esteem issues for children/fathers/parents; d. DNA copied/amplified using PCR; e. DNA cut using restriction enzymes; f. (gel) electrophoresis used to separate DNA fragments; g. pattern of bands is produced (in gel); h. analysed for matches between child with mother and possible father; i. (about) half the child's bands will match the father (while the other half will match the mother);
Explain how hormones are used to control the human menstrual cycle.
a. FSH stimulates the development of follicles b. follicles produce estrogen c. estrogen stimulates the repair of the uterus lining d. estrogen stimulates LH secretion e. LH causes/stimulates ovulation f. LH causes/stimulates the development of the corpus luteum g. corpus luteum secretes progesterone h. progesterone causes/stimulates thickening of the uterus lining OR prepares uterine lining for implantation OR maintains the endometrium i. progesterone/estrogen inhibits the secretion of LH/FSH j. falling progesterone levels at the end of the cycle allow FSH production/menstruation k. negative/positive feedback «control» described correctly l. LH/FSH are pituitary hormones
Describe the polymerase chain reaction (PCR), including the role of Taq DNA polymerase.
a. PCR is process by which a small sample of DNA can be amplified/copied many times b. PCR involves repeated cycling through high and lower temperatures «to promote melting and annealing of DNA strands» c. «mixture» is heated to high temperatures to break «hydrogen» bonds between strands of DNA/to separate the double-stranded DNA d. Taq DNA polymerase can withstand high temperatures without denaturing e. primers bind to «targeted» DNA sequences at lower temp f. Taq DNA polymerase forms new «double-stranded» DNA by adding «complementary» bases/nucleotides
Outline natural methods of cloning in some eukaryotes.
a. clones are genetically identical organisms OR group of cells derived from a single parent cell b. asexual reproduction in plants such as tubers/runners/bulbs Allow other verifiable examples of plants c. common in non-vertebrates such as budding in hydra Allow other verifiable examples of invertebrates d. budding in yeast/fungi Allow other verifiable examples of fungi e. identical twins «in humans» are clones because they originate fromthe same cell
Describe the process of blood clotting.
a. clotting factor released by platelets/damaged tissue/cells; b. cascade/series of reactions; c. prothrombin (activated) to thrombin; d. soluble fibrinogen to insoluble fibrin / thrombin converts fibrinogen to fibrin; e. mesh of fibrin/fibres seals wound/traps platelets/red blood cells;
Define codominant allele, recessive allele, locus and sex linkage.
a. codominant allele: (pair of) alleles that both affect the phenotype when present in a heterozygote / both alleles are expressed; b. recessive allele: an allele that produces its characteristic phenotype only when present in homozygous state / is expressed when dominant allele not present; c. locus: the (particular) position of a gene on a chromosome/homologous chromosomes; d. sex linkage: a gene located on a sex chromosome/X/Y/X or Y chromosome;
Explain the inheritance of colour blindness.
a. colour blindness caused by recessive allele / colour blindness is recessive; b. gene located on X chromosome/sex-linked; c. Xb is allele for colour blindness and XB is allele for normal colour vision/dominant allele; d. male has one X and one Y chromosome; e. male has only one copy of gene(s) located on X chromosome; f. X chromosome (in males) comes from female parent; g. any male receiving allele from mother will express the trait; h. XbY is genotype for colour blind male; i. many more males have colour blindness than females; j. female will express colour blindness only if is homozygous recessive/Xb Xb; k. heterozygous/XB Xb female is a carrier; l. colour blind female could be born to colour blind father and carrier mother;
Outline the use of named enzymes in gene transfer using plasmids.
a. plasmids are removed/obtained from bacteria; b. endonuclease/restriction enzymes cut the plasmids at target sequences; c. DNA fragments of other organism are cut with the same restriction enzymes; d. in both DNA and plasmid, complementary sticky ends/staggered cut are produced; e. DNA segment added to the opened plasmid; f. spliced together by ligase; g. reverse transcriptase makes DNA copies of mRNA / DNA polymerase to increase the amount of DNA; h. recombinant plasmids inserted into new/host cells; i. cultured/cloned to produce the new genes/more genetically modified cells;
Following fertilization, cells in the developing embryo differentiate. Outline a technique for cloning using differentiated animal cells.
a. differentiated/somatic/diploid cells taken from donor animal/sheep udder; b. (diploid) nucleus from donor cells removed; c. ova/eggs cells removed from (donor) animal/female sheep; d. (haploid) nucleus removed from eggs/ova; e. (diploid/donor's) nucleus is fused with/inserted into egg/ovum (to form zygote); f. embryo (from cell with donor nucleus and egg from surrogate) implanted in uterus of surrogate mother; g. normal pregnancy and birth is completed; h. offspring is a genetic copy/clone of the donor mother/diploid nucleus WTTE;
Explain how males inherit hemophilia and how females can become carriers for the condition.
a. hemophilia is due to a recessive allele/is a recessive trait / XH is normal allele and Xh is hemophilia allele; b. hemophilia is sex linked; c. allele/gene is on the X chromosome;Reject disease/hemophilia carried on X chromosome. d. (sex chromosomes in) females are XX while males are XY; e. Y chromosomes do not have the allele/hemophiliac males are XhY; f. males inherit their X chromosome from their mother/do not pass the allele to sons; g. males have only one copy so recessive trait/allele is not masked; h. males have a 50% chance of hemophilia/receiving the allele if mother is a carrier; i. carrier is heterozygous for the gene/is XHXh; j. dominant/normal allele masks the recessive allele (so clotting is normal); k. females inherit one X chromosome from father and one from mother; l. affected/hemophiliac males have carrier daughters; m. hemophilia allele could have been inherited from either parent;
Factor IX is a blood clotting protein which some hemophiliacs lack. In the future hemophilia could be treated using clotting factors synthesized by genetically modified bacteria. Outline the basic technique used for this gene transfer.
a. mRNA/gene coding for factor IX extracted from human cell/tissue; b. mRNA copied to DNA/cDNA (using reverse transcriptase); c. plasmids used (for gene transfer); d. restriction enzyme/endonuclease used to open plasmid/cut DNA; e. complementary bases/sticky ends on gene and plasmid/link gene to plasmid; f. sealed using ligase; g. recombinant plasmid/plasmid containing desired gene taken up by bacteria; h. isolate/clone the recombinant/transformed bacteria; i. bacteria cultured/grown in fermenter to produce factor IX;
Meiosis in humans produces cells that participate in fertilization. Outline the processes involved in meiosis.
a. meiosis reduces a diploid cell into (four) haploid cell(s); b. (during prophase I) homologous chromosomes pair up/synapsis; c. chromatids (break and) recombine / crossing over d. (metaphase I) (homologous chromosomes) at the equator of the spindle / middle of cell; e. (anaphase I) (homologous) chromosomes separate and move to opposite poles; f. (telophase I) chromosomes reach poles and unwind WTTE; g. (prophase II) chromosomes (condense and) become visible, new spindles form; h. (metaphase II) chromosomes line up at the centre of the cells/equator; i. (anaphase II) sister chromatids separate; j. (telophase II) chromatids reach the poles and unwind;
Describe the origin of eukaryotic cells according to the endosymbiotic theory.
a. mitochondria and chloroplasts are similar to prokaryotes b. «host» cell took in another cell by endocytosis/by engulfing «in a vesicle» Allow "taking in" in place of "engulfing" c. but did not digest the cell/kept the «ingested» cell alive OR symbiotic/mutualistic relationship «between engulfed and host cell» d. chloroplasts and mitochondria were once independent/free-living «organisms» e. DNA «loop» in chloroplast/mitochondrion f. division/binary fission of chloroplast/mitochondrion g. double membrane around chloroplast/mitochondrion h. 70s ribosomes «in chloroplast/mitochondrion»
Using a named example of a genetically modified crop, discuss the specific ethical issues of its use.
a. named example of verified genetically modified crop; eg, Bt corn / golden rice; b. Maize crops (Bt corn) have been engineered to be toxic to the corn borer by introducing a toxin gene from a bacterium (Bacillus thuringiensis) There are benefits and harmful effects d. increased crop yields e. reduced need for use of chemical pesticides; f. ingestion of toxin by nontarget species; g. concerns about contamination of neighbouring non-GMO crops affecting trade;
Explain chemiosmosis as it occurs in photophosphorylation.
a. photophosphorylation is the production of ATP;b. (some of the) light absorbed by chlorophyll / photosystem II;c. photolysis/splitting of water separation of hydrogen ion from its electron; d. the electron transport system moves the electrons through a series of carriers; e. (electron transport system occurs) in the thylakoid membrane; f. electron transport linked to movement of protons into thylakoid space; g. a proton gradient builds up (in the thylakoid space);h. small thylakoid space enhances the gradient; i. hydrogen ions move by diffusion through the ATP synthase; j. ADP + inorganic phosphate (Pi) forms ATP; k. (the kinetic energy from) movement of hydrogen ions (through ATP synthase) generates ATP; l. ATP synthase is a protein complex in the thylakoid membrane; m. formation of proton gradient / ATP synthesis linked to electron transport is chemiosmosis;
Outline a technique used for gene transfer.
a. plasmid used for gene transfer/removed from bacteria; b. plasmid is a small/extra circle of DNA; c. restriction enzymes/endonucleases cut/cleave DNA (of plasmid); d. each restriction enzyme cuts at specific base sequence/creates sticky ends; e. same (restriction) enzyme used to cut DNA with (desired) gene; f. DNA/gene can be added to the open plasmid/sticky ends join gene and plasmid; g. (DNA) ligase used to splice/join together/seal nicks; h. recombinant DNA/plasmids inserted into host cell/bacterium/yeast;
State one type of environmental factor that may increase the mutation rate of a gene.
a. radiation b. chemical mutagens/carcinogens/papilloma virus/cigarette smoke
Discuss ethical issues of therapeutic cloning in humans.
a. therapeutic cloning involves producing embryos from which embryonic stem cells can be harvested for medical use; argument in favour: b. (to many people) any procedure that reduces pain and suffering is ethically/morally justified; c. stem cells can be used to replace organs/tissues that have been lost/damaged in a patient; d. (thus) pain and suffering can be reduced/lives can be saved/life quality improved; e. cells can be removed from embryos that have stopped developing and would have died anyway; f. cells are removed at a stage when no pain can be felt by the embryo; g. use embryos from IVF that would otherwise be destroyed; argument against: h. embryonic stem cells are no longer needed as adult stem cells can be used without causing loss of life; i. there is danger of embryonic stem cells developing into tumour cells/harmful effects are not yet known; j. every human embryo is a potential human with the right to development; k. more embryos may be produced than can be used and so some would be killed; l. (to many people) any procedure that harms a life/kills is unethical/morally wrong;
Outline how translation depends on complementary base pairing.
a. translation converts a sequence of mRNA nucleotides/codons to a sequence of amino acids/polypeptide/protein b. «triplets of» nucleotides/bases on «activated» tRNAs pair with complementary «triplets of» nucleotides/bases on mRNA / vice versa c. base pairing occurs when adenine/A pairs with uracil/U and guanine/G pairs with cytosine/C d. specific amino acids are attached to specific of tRNA e. mRNA has codons AND tRNA has anticodons
Explain how evolution may happen in response to environmental change with evidence from examples.
a. variation in population; b. (variation is) due to mutation/sexual reproduction; c. valid example of variation in a specific population; d. more offspring are produced than can survive / populations over-populate; e. competition / struggle for resources/survival; f. example of competition/struggle for resources; g. survival of fittest/best adapted (to the changed environment)/those with beneficial adaptations / converse; h. example of changed environment and adaptation to it; i. favourable genes/alleles passed on / best adapted reproduce (more) /converse; j. example of reproduction of individuals better adapted to changed environment; k. alleles for adaptations to the changed environment increase in the population; l. example of genes/alleles for adaptations increasing in a population; m. evolution by natural selection; n. evolution is (cumulative) change in population/species over time / change in allele frequency;
Identify one type of gene mutation.
base substitution/insertion/deletion/frameshift
Explain why carriers of sex-linked (X-linked) genes must be heterozygous.
carrier has (one copy of) a recessive allele; must also have a dominant allele to prevent having the condition/disease; or cannot be homozygous dominant or they would not carry the recessive allele; cannot be homozygous recessive or they would have the condition/disease;
Explain the causes of sickle-cell anemia.
caused by gene mutation; (sickle-cell anemia) due to a base substitution (mutation); changes the code on the DNA; which leads to a change in transcription / change in mRNA; DNA changes from CTC to CAC/GAG to GTG / mRNA changes from GAG to GUG; (accept DNA changes from CTT to CAT/GAA to GTA / mRNA changes from GAA to GUA) which (in turn) leads to a change in translation / change in polypeptide chain/ protein; (the tRNA) adds the wrong amino acid to the polypeptide chain; glutamic acid replaced by valine; produces abnormal hemoglobin; causing abnormal red blood cell/erythrocyte shape / sickle shape; which lowers the ability to transport oxygen; sickle-cell allele is codominant; homozygote/HbS HbS have sickle cell anemia/is lethal / heterozygote/HbS HbA has the sickle trait/is carrier (and is more resistant to malaria);
Describe karyotyping and one application of its use.
cells undergoing mitosis are used for karyotyping; process of mitosis is stopped at (mitotic) metaphase; chromosomes (cut from photographs) are arranged in pairs of similar structure/ homologous chromosomes; allows abnormalities in the chromosome number/appearance to be seen; any valid example (e.g. in Down syndrome / gender of fetus); detected by identifying unique feature (e.g. trisomy 21 / one extra chromosome / 47 chromosomes);
Discuss the potential benefit and possible harm of one named example of gene transfer between species.
gene transfer details Bt gene transferred from bacterium/Bacillus to maize specific benefit: corn borer/insect pest killed by Bt toxin increasing crop production; less pesticides/fertilizers/chemicals needed so better for environment; specific harmful effect: non-target insects may be killed as well; risk of cross-pollination may introduce gene to unintended species;
Outline a technique of gene transfer resulting in genetically modified organisms.
gene transfer takes a gene from one species/organism and inserts it into another; using plasmid/viral vector/ballistic impregnation/electroporation; use of reverse transcriptase to obtain gene from mRNA; restriction enzyme/endonuclease used to cut out/excise gene; (same) restriction enzyme used to cut open plasmid; sticky ends used to link DNA/link gene to plasmid; DNA ligase used to seal nicks/splice; bacterium takes in plasmid / plasmid transferred to bacterium/plant/host cell; valid documented example (e.g. human insulin from bacterium/yeast / salt-tolerant tomato plant / carotene/vitamin A in rice /herbicide/Roundup/glyphosate resistance in crop plants / factor IX/clotting factor in sheep milk / low phosphate feces in pigs;
Outline the inheritance of a named sex-linked condition in humans.
genes that are located on just one of the sex chromosomes/X or Y are sex-linked; (sex-linked) genes present on the X chromosome are absent from the Y chromosome / vice versa; named recessive X-linked condition (e.g. colour blindness / haemophilia / other valid example); sex-linked conditions tend to be more commonly expressed in males; female can be homozygous or heterozygous/carrier for a sex-linked/X-linked condition; affected males have only one copy of the gene / have carrier daughters but cannot pass the condition on to sons; carrier/heterozygous females can have affected sons/carrier daughters; for a female to be affected (homozygous recessive) the father must be affected;
The genes described above form a linkage group. Define linkage group.
genes that are located on the same chromosome (form a linkage group)
Using a named example, discuss the benefits and harmful effects of genetic modification.
genetic modification is when the DNA/genotype of an organism is artificially changed; genetic modification alters some characteristic/phenotype of the organism; named example with modification (e.g. salt tolerance in tomato plants); benefits: [5 max] allows crops to be grown where they would not grow naturally; provides more food; economic benefits; expands world's productive farmland; reduces the need to clear rainforests to grow crops; lowers cost of production; less pesticides/fertilizers/chemicals needed so better for environment; Award marks for any valid benefit consistent with a named example. harmful effects: [5 max] may be released into natural environment; may affect food chains / unintended effects on other organisms; may affect consumers e.g. allergies/health risks; unfair to smaller farmers who cannot compete; long-term effects are unknown; risk of cross-pollination; risk of long-term contamination of soil;
Explain, using a named example, how polygenic inheritance gives rise to continuous variation.
human skin colour can vary from pale to very dark / amount of melanin varies; skin colour/melanin controlled by (alleles from) at least three/several genes; no alleles are dominant / alleles are co-dominant / incomplete dominance; many different possible combinations of alleles; skin colour controlled by cumulative effect/combination of genes/alleles;
Explain benefits and risks of using genetically modified crops for the environment and also for human health.
nvironment benefits: a. pest-resistant crops can be made b. so less spraying of insecticides/pesticides c. less fuel burned in management of crops d. longer shelf-life for fruits and vegetables so less spoilage e. greater quantity/shorter growing time/less land needed f. increase variety of growing locations / can grow in threatened conditions Environment risks: g. non-target organisms can be affected h. genes transferred to crop plants to make them herbicide resistant could spread to wild plants making super-weeds i. GMOs (encourage monoculture which) reduces biodiversity j. GM crops encourage overuse of herbicides Health benefits: k. nutritional value of food improved by increasing nutrient content l. crops could be produced that lack toxins or allergens m. crops could be produced to contain edible vaccines to provide natural disease resistance Health risks: n. proteins from transferred genes could be toxic or cause allergic reactions o. antibiotic resistance genes used as markers during gene transfer could spread to «pathogenic» bacteria p. transferred genes could cause unexpected/not anticipated problems OR health effects of exposure to GMO unclear
Explain the effect of changes of pH, substrate concentration and temperature on enzyme activity.
pH: a. enzymes have an optimal pH/work best at a given ; b. activity increases as pH gets closer to optimal pH; c. extreme pH denatures enzymes; d. by breaking bonds / changing enzyme shape/structure / active site shape/structure; substrate: e. as substrate concentration increases, activity increases; f. as substrate concentration increases, the collisions between substrate and enzyme increase; g. up to a maximal level of action / reaching a plateau; h. all active sites are saturated/occupied; temperature: i. enzymes have an optimal temperature (where they work most effectively); j. activity increases as it gets closer to optimal temperature; k. high temperatures stop enzyme activity due to irreversible changes in structure / denaturation; l. by breaking bonds / changing enzyme shape/structure / active site shape/structure;
Outline a basic technique for gene transfer.
plasmid removed from bacteria; plasmid cleaved/cut open by restriction enzymes; desired gene/DNA extracted from donor; DNA from donor cleaved using same restriction enzyme; results in sticky ends; with complementary base sequences; pieces of DNA from two organisms mixed; ligase used to splice pieces (DNA); recombinant plasmids formed; insertion into host cells;
Hemophilia is a disorder where the ability to control blood clotting or coagulation is impaired. Describe the process of blood clotting.
release of clotting factors from platelets/damaged cells; conversion of prothrombin to thrombin; thrombin catalyses the conversion of fibrinogen into fibrin; (insoluble) fibrin (net) captures blood cells;
State two general types of enzymes used in gene transfer.
restriction enzymes / endonucleases; ligases; reverse transcriptase;
Describe a technique used for gene transfer.
restriction enzymes/endonucleases cut a small fragment of DNA from an organism; same restriction enzymes used to cut DNA of plasmid / e.g. E. coli; sticky ends are the same in both cases; fragment of DNA is inserted into the plasmid; spliced together by ligase; to make recombinant DNA/plasmids; recombinants can be inserted into host cell and cloned;
Describe the inheritance of colour blindness in humans.
sex linked condition; carried on an X chromosome / absent from Y chromosome; if present in male causes colour blindness; (allele is) recessive so heterozygous females are not colour blind; homozygous females are colour blind;
Outline the inheritance of hemophilia in humans.
sex-linked/on X chromosome; recessive allele / Xh; more common in males than females; heterozygous females are carriers / only females can be carriers;
Describe how human skin colour is determined genetically.
skin colour is an example of polygenic inheritance; many/more than two genes contribute to a person's skin colour; due to the amount of melanin in the skin; combination of alleles determines the phenotype; allows for range of skin colours / continuous variation of skin colour; phenotypes do not follow simple Mendelian ratios of dominance and recessiveness; the environment also affects gene expression of skin colour / sunlight/UV light stimulate melanin production; the more recessive alleles there are, the lighter the skin colour; (vice versa)
State the source, substrate, products and optimal pH condition for lipase in the human digestive system.
source: pancreas; substrate: triglycerides / lipids / fats / oils; product: glycerol and (three) fatty acids; (both needed) optimal pH: 8; (accept answers in the range of 7 to 8)
Explain the role of transfer RNA (tRNA) in the process of translation.
tRNA attaches to (specific) amino acid; tRNA (with amino acid) moves to the ribosome; anticodon of tRNA binds with codon of mRNA;
In the pea plant (Pisum sativum), the allele for tall plants is A and the allele for short plants is a. The allele for green plants is B and the allele for yellow plants is b. Determine the phenotype of Aabb.
tall and yellow
Explain the process of translation.
translation is the synthesis of proteins/polypeptide chain/specific sequence of amino acids; translation occurs in cytoplasm/ribosomes; uses information on the mRNA; mRNA carries the genetic information of DNA; mRNA binds to ribosome; mRNA contains series of codons/base triplets; tRNA binds with an amino acid and carries it to the ribosome; tRNA has the anticodon that is complementary to the codon on the mRNA; two tRNAs bind to a ribosome/mRNA at the same time; (peptide) bond forms between two amino acids (carried by tRNA molecules to the ribosome); the first tRNA detaches, ribosome moves along mRNA and another tRNA carrying an amino acid binds; process repeats forming chain of amino acids/polypeptides;
Describe the role of sex chromosomes in the control of gender and inheritance of hemophilia.
two sex chromosomes are X and Y; one sex chromosome inherited from each parent; XX results in female;XY results in male; sex determined by sperm/father; sex-linked genes are those located on the sex chromosomes / usually refers to genes on X chromosome; recessive sex-linked traits appear more frequently in males since they only have one X chromosome; hemophilia is an example of a gene located on the X chromosome/sex-linked; female carriers are heterozygous / XHXh; males with hemophilia are XhY / normal males are XHY; sons (of carrier females) have 50 % probability of showing the trait (even if father is normal); daughters (XhXh) of hemophiliac father and carrier mother can be affected / daughters who receive an affected X from each parent will have hemophilia;