IB Biology HL - Unit 6: Genetics

Creeper in chickens is a condition in which the chickens are born with very short legs. The creeper allele (C) is dominant over the normal allele (c). Embryos which are homozygous for the dominant allele fail to develop into viable chickens and die before they hatch. What phenotypic ratio would you expect in the live offspring of a cross between two creeper chickens? - All creeper - 1 creeper; 2 normal - 2 creeper; 1 normal - 3 creeper; 1 normal

- 2 creeper; 1 normal

In humans, male pattern baldness is caused by a recessive sex-linked gene found only on the X chromosome. If a father who does not have male pattern baldness and a mother who is a carrier for it have a child, what is the probability that the child will develop male pattern baldness in adulthood? - 0 % - 25 % - 50 % - 75 %

- 25 %

The micrographs show four different phases from meiosis II. What is the correct order? - 4-2-3-1 - 2-3-4-1 - 4-3-2-1 - 3-4-2-1

- 4-3-2-1

In cats, black coat colour is dominant over gray. A female black cat, whose mother is gray, mates with a gray male. What is the predicted ratio of phenotypes in the offspring? - 100 % black - 50 % black to 50 % gray - 75 % black to 25 % gray - 100 % gray

- 50 % black to 50 % gray

Huntington's disease is an autosomal dominant genetic disease. What are the chances of two parents that are heterozygous for the gene having a child with Huntington's disease? - 25 % - 50 % - 75 % - 100 %

- 75 %

The pedigree chart shows the inheritance of hemophilia in some of the descendants of Queen Victoria. Which letter points to a family member certain to be heterozygous? - A - B - C - D

- A

What is always passed to the next generation as a result of sexual reproduction? - Homologous chromosomes from the mother - A haploid set of chromosomes from the mother - A chromatid from every chromosome of the father - All alleles from each parent

- A haploid set of chromosomes from the mother

Tall heterozygous pea plants were crossed and the resulting seeds grown. Out of 360 plants, 270 were tall and 90 dwarf. What describes the expected genotypes resulting from the cross? - All 270 tall plants were heterozygous. - All 270 tall plants were homozygous. - Only 90 plants were homozygous. - All dwarf plants were homozygous.

- All dwarf plants were homozygous.

Chromosome numbers vary between species. Which statement refers to humans? - A zygote has two autosomes. - An egg cell has 22 autosomes. - A sperm cell has 23 autosomes. - An egg cell has two X chromosomes.

- An egg cell has 22 autosomes.

What forms when two different chromatids of the same homologous pair cross over? - Telomere - Chiasma - Chromosome mutation - Daughter centromere

- Chiasma

What is produced by meiosis in a cell of a male animal? - Two gametes, each with the same number of chromosomes - Four gametes, each with different numbers of chromosomes - Two gametes, each with different numbers of chromosomes - Four gametes, each with the same number of chromosomes

- Four gametes, each with the same number of chromosomes

Which event occurs in the first division of meiosis? - Synthesis of DNA - Pulling apart of sister chromatids - Halving of the chromosome number - Division of centromeres

- Halving of the chromosome number

When a cell divides by meiosis, chiasmata can be observed. Which are features of chiasmata? I. They are points of attachment between chromatids of non-homologous chromosomes. II. They occur during meiosis I. III. They increase genetic diversity of bivalents. - I, II and III - II and III only - I and II only - I and III only

- II and III only

Some breeds of dogs are characterized by the presence of a melanistic mask, which is a darkening of the fur near the nose. Which outcome is matched with a valid conclusion if dogs that were pure breeding for melanistic masks were crossed with dogs without melanistic masks? - If 0 % of the puppies have a mask, the character is recessive. - If 25 % of the puppies have a mask, the character is dominant. - If 75 % of the puppies have a mask, the character is dominant. - If 100 % of the puppies have a mask, the character is recessive.

- If 0 % of the puppies have a mask, the character is recessive.

Where can the entire genome of an organism be found? - In the DNA present in the nucleus and chloroplasts of a plant cell - In the DNA present in the nucleus and mitochondria of an animal cell - In the DNA present in plasmids of a bacterial cell - In the DNA present in the nucleus of a eukaryotic cell

- In the DNA present in the nucleus and mitochondria of an animal cell

The pedigree chart shows the inheritance of hemochromatosis, a genetic disease which causes an excessive accumulation of iron in the body. What can be deduced about this genetic disease from the pedigree chart? - It is sex-linked. - It is autosomal dominant. - It is autosomal co-dominant. - It is autosomal recessive.

- It is autosomal recessive.

The diploid number of chromosomes in humans (Homo sapiens) is 46 and the diploid number of chromosomes in rice (Oryza sativa) is 24. What does this indicate about diploid chromosome numbers? - The evolutionary progress of species is determined by the diploid number of chromosomes. - Members of a species have the same diploid number of chromosomes. - The complexity of the organisms is correlated to the diploid number of chromosomes. - Plant species have a lower diploid number of chromosomes than animals.

- Members of a species have the same diploid number of chromosomes.

Which process occurs in meiosis but not in mitosis? - Movement of homologous chromosomes to opposite ends - Replication of DNA prior to the start of cell division - Attachment of spindle fibres to the centromeres of each chromosome - Separation of sister chromatids during anaphase

- Movement of homologous chromosomes to opposite ends

Which statement applies to meiosis and mitosis? - Meiosis occurs in a greater number of locations in the body compared to mitosis. - Recombination occurs in both meiosis and mitosis. - Reduction in chromosome number occurs in both meiosis and mitosis. - Separation of chromatids occurs in both meiosis and mitosis.

- Separation of chromatids occurs in both meiosis and mitosis.

Which event happens in meiosis II but not in meiosis I? - Sister chromatids move to opposite poles. - Chromosomes become shorter and thicker by coiling. - Spindle microtubules attach to centromeres. - Crossing over occurs.

- Sister chromatids move to opposite poles.

The graph shows the incidence of trisomy resulting from non-disjunction in pregnancies at different maternal ages. What can be inferred from the graph? - The incidence of three copies of a chromosome increases the most from age 35. - The incidence of three copies of a chromosome increases directly in proportion with the age of the mother. - The incidence of three sets of chromosomes increases from age 20. - The incidence of three sets of chromosomes increases the most from age 30.

- The incidence of three copies of a chromosome increases the most from age 35.

The system of sex determination in chimpanzees (Pan troglodytes) is the same as in other mammals. A chimpanzee has 48 chromosomes in the nuclei of its body cells. What can be deduced from this information? - The sex of the chimpanzee - Whether non-disjunction has occurred - The number of genes in each chromosome - The number of autosomes in a diploid cell

- The number of autosomes in a diploid cell

The karyogram shown belongs to a human being. What can be deduced from this karyogram? - The person is a male with a genetic disorder. - The person is a male with Down syndrome. - The person is a female with Down syndrome. - The person is a female with a missing chromosome.

- The person is a male with a genetic disorder.

The image shows a karyogram. What information can be determined from this karyogram? - The species is not human. - The sex is female. - Disjunction occurred during meiosis. - The haploid number is 54.

- The species is not human.

What is a difference between two alleles of a gene? - The characteristics they influence - Their base sequence - Their amino acid sequence - Their positions on homologous chromosomes

- Their base sequence

For what purpose is a karyogram used? - To identify the genome size of a species - To identify linked genes in the chromosomes of an individual - To identify chromosomal abnormalities in an individual - To identify gene loci in a species

- To identify chromosomal abnormalities in an individual

The electron micrograph shows a section through a plant cell. In which structure(s) is the genome of the cell contained? - X, Y and Z only - Z only - W and X only - X and Y only

- X, Y and Z only

What contributes to genetic variation?

1. Independent assortment - separate genes for separate traits are passed independently of one another from parents to offspring. 2. Crossing over - parts of the two chromosomes are switched; the chromosomes contain the same genes, but may have different forms of the genes. 3. Random Fertilization - each parent is capable of producing a huge variety of genetically different gametes and the number of possible combinations among their offspring is large. 4. Mutations - changes is base sequences result in different traits.

Describe Telophase II.

A new nuclear membrane forms around chromosomes and the two cells split into 4 cells.

Which pedigree chart is consistent with the inheritance of red-green colour blindness? (Picture) A. B. C. D.

A.

What is thought to be the origin of most new alleles? A. A mutation B. An infection C. Protein synthesis D. DNA replication

A. A mutation

Which of the statements best describes "Alleles"? A. Different forms of a gene. B. Parts of a chromosome containing genes. C. Pairs of factors which make up genes. D. Different genes on a chromosome.

A. Different forms of a gene.

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. Half of the children

What feature of eukaryotic chromosomes distinguishes them from the chromosomes of prokaryotes? A. Histone proteins B. Circular DNA C. Double-stranded DNA molecules D. Multiple genes along the length of each chromosome

A. Histone proteins

What is the effect of dominant alleles? I. They mask the effect of recessive alleles. II. They become more frequent than recessive alleles in a population. III. They have a joint effect with recessive alleles when characteristics are co-dominant. A. I only B. I and II only C. I and III only D. I, II and III

A. I only

A couple have four children whose blood groups are A, B and AB. What is the likely combination of the parents' genotypes? A. IAi and IBi B. IAi and IBIB C. IAIB and ii D. IAIA and IBIB

A. IAi and IBi

What information can be concluded from the karyotype? A. The person is a normal male. B. The person is a normal female. C. The person is a male with Down syndrome. D. The person is a female with Down syndrome.

A. The person is a normal male.

Which is a characteristic of the pairs of sister chromatids that are visible during meiosis? A. They result from the replication of DNA before meiosis. B. They are only present in meiosis I. C. They split apart during metaphase I in meiosis. D. They are only present in meiosis II.

A. They result from the replication of DNA before meiosis.

What is the Law of Segregation?

Allele pairs separate during gamete formation and randomly unite at fertilization.

The diagram shows a pedigree of cystic fibrosis, in which the black colour indicates the presence of cystic fibrosis. What is the probability that the individual labelled X is a carrier of cystic fibrosis? A. 1.00 B. 0.50 C. 0.25 D. 0.00

B. 0.50

A dominant autosomal allele for lactase persistence allows humans to digest milk as adults. People who lack this allele are lactose intolerant into adulthood. If J and K have a child L, what is the probability that L will be lactase persistent? A. 25% B. 50% C. 75% D. 100%

B. 50%

Which statement is valid regarding chromatids? A. Sister chromatids separate during meiosis I. B. Chiasmata form between non-sister chromatids. C. Crossing over is the exchange of DNA between sister chromatids only. D. Non-sister chromatids have the same combination of alleles.

B. Chiasmata form between non-sister chromatids.

What is a characteristic of the human Y chromosome? A. It is made of DNA and histones covered by phospholipids. B. It contains some genes that are not present on the X chromosome. C. It is the largest chromosome in the human karyotype. D. It has a condensed length of approximately 100 μm.

B. It contains some genes that are not present on the X chromosome.

Which is a characteristic of the haploid number of eukaryotic chromosomes? A. It doubles in mitosis. B. It is fixed for each species. C. It is an even number for all species. D. It is positively correlated with an animal's mass.

B. It is fixed for each species.

If there are 16 chromosomes in a cell that is about to divide, what will be the number of chromosomes in a daughter cell after division by mitosis or meiosis? A. Mitosis: 16, Meiosis: 16 B. Mitosis: 16, Meiosis: 8 C. Mitosis: 8, Meiosis: 16 D. Mitosis: 8, Meiosis: 8

B. Mitosis: 16, Meiosis: 8

At which stage of meiosis are bivalents formed? A. Interphase B. Prophase I C. Prophase II D. Metaphase II

B. Prophase I

Which genotype would be normally found in a gamete? A. Rr B. RS C. rStt D. TUt

B. RS

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 pal-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. The two genes are linked.

What is a characteristic of homologous chromosomes? A. They have an identical DNA sequence. B. They are of the same length in karyograms. C. They form pairs in prokaryotes. D. They carry the same alleles.

B. They are of the same length in karyograms.

What is the chromosome number in a human gamete with non-disjunction? A. 46 B. 45 C. 24 D. 23

C. 24

Many genes control cat coat colour. Tabby cats have a coat with stripes. Two of their genes are the tabby gene Mm and the agouti gene Aa. The dominant allele M codes for straight stripes, whereas the recessive allele m codes for blotches and whorls instead of stripes. The dominant allele A produces two-toned hair, to reveal coat patterns, whereas the recessive allele a causes all coat hair to be black and so hides any pattern. In a cross between two double heterozygous tabby cats, what would the expected proportion of black offspring be? A. 1 out of 16 B. 3 out of 16 C. 4 out of 16 D. 9 out of 16

C. 4 out of 16

Which of the statements below is the best definition of "a gene"? A. A heritable factor which makes a protein. B. The location on a chromosome of a specific length of DNA. C. A heritable factor made of a length of DNA which influences a specific characteristic. D. All the genetic information in an organism.

C. A heritable factor made of a length of DNA which influences a specific characteristic.

What are all the possible phenotypes of children born to a mother with blood group AB and a father with blood group B? A. AB only B. A and B C. AB, A and B D. AB, A and O

C. AB, A and B

An individual is heterozygous for two linked genes AB | ab. To investigate the frequency of crossing over, a test cross is carried out between the individual and another that is homozygous recessive for both genes. What are the possible recombinants in the offspring of this cross? A. Ab | | ab and Ab | | ab B. AB | | ab and Ab | | aB C. Ab | | ab and aB | | ab D. AA | | aa and BB | | bb

C. Ab | | ab and aB | | ab

Which biological term refers to the different forms of a gene which differ by just a few bases? A. Proteomes B. Genes C. Alleles D. Genotypes

C. Alleles

What distinguishes an allele from a gene? A. An allele is made of RNA. B. An allele is shorter. C. An allele is a variety of a gene. D. An allele cannot be transferred during genetic modification.

C. An allele is a variety of a gene.

Black, short-haired guinea pigs, heterozygous for both characteristics, were crossed. They produced offspring with the phenotypes black short-haired, black long-haired, white short-haired and white long-haired in the ratio 9:3:3:1. A different cross produced offspring with phenotypes in the ratio 1:1:1:1. What were the genotypes of the parents in the second cross? A. BbSs x BbSs B. BBSs x BbSS C. BbSs x bbss D. bbSS x BBsS

C. BbSs x bbss

What is the name given to a heritable factor which controls a specific characteristic? A. Allele B. Chromosome C. Gene D. Mutation

C. Gene

What maximum number of different genotypes and phenotypes are possible among the children of a mother with blood group A and a father with blood group B? A. Genotypes: 2, Phenotypes: 2 B. Genotypes: 2, Phenotypes: 4 C. Genotypes: 4, Phenotypes: 4 D. Genotypes: 4, Phenotypes: 2

C. Genotypes: 4, Phenotypes: 4

A variety of Pelargonium has yellow leaves. When plants of this variety are crossed, the resulting seeds produce green, yellow and white seedlings in the ratio 1 : 2 : 1. If plants with yellow leaves are crossed with plants with green leaves, what would the expected ratio of phenotypes in the offspring be? A. Green: 1, Yellow: 2, White: 1 B. Green: 3, Yellow: 1, White: 0 C. Green: 2, Yellow: 2, White: 0 D. Green: 2, Yellow: 1, White: 1

C. Green: 2, Yellow: 2, White: 0

A gene is a heritable factor. What is it made from? A. Made from protein. B. Made from the genome of a cell. C. Made of a length of DNA. D. Made from a specific length of mRNA.

C. Made of a length of DNA.

What causes the presence of three chromosomes 21 in Down syndrome? A. Crossing over B. Allele change C. Non-disjunction D. Gene mutation

C. Non-disjunction

In fruit flies (Drosophila melanogaster), grey bodies (b+) are dominant to black bodies (b) and normal wings (vg+) are dominant to vestigial wings (vg). Homozygous vestigial winged, black bodied flies were crossed with individuals that were heterozygous for both traits. 2300 individuals were counted and the phenotypes observed were recorded as shown. 965 normal wings, grey bodies 944 vestigial wings, black bodies 206 vestigial wings, grey bodies 185 normal wings, black bodies Which statement is valid? A. The predicted phenotypic ratio was 9:3:3:1. B. There is independent assortment of wings but not body colour. C. The expected number of vestigial winged, grey bodied flies was 575. D. The traits are on different chromosomes.

C. The expected number of vestigial winged, grey bodied flies was 575.

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. The genes in the genetic crosses were linked.

What proves that the inheritance of the condition shown in this pedigree chart is autosomal recessive and not autosomal dominant? A. There is no affected person in generation I. B. Both males and females are affected. C. Two unaffected parents have a child that is affected. D. Not everybody in generation III is affected.

C. Two unaffected parents have a child that is affected.

Describe Metaphase II.

Chromosomes line up at the center of the cell at the metaphase plate.

A body cell of a goat has 60 chromosomes. What would be produced following meiosis in the testis of a male goat? A. 2 cells each with 60 chromosomes. B. 4 cells each with 60 chromosomes. C. 2 cells each with 30 chromosomes. D. 4 cells each with 30 chromosomes.

D. 4 cells each with 30 chromosomes.

How does meiosis cause Mendel's law of independent assortment? A. Linked genes are randomly separated. B. The chromosome number is divided twice. C. Crossing-over occurs in Anaphase I. D. Alleles that are not in the same linkage group are segregated.

D. Alleles that are not in the same linkage group are segregated.

At which stage of meiosis does a pair of sister chromatids separate? A. Metaphase I B. Anaphase I C. Metaphase II D. Anaphase II

D. Anaphase II

The genetic determination of dogs' coats can be quite complex, with many 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 color. 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. Eebb

Which disease is an example of sex-linked (X-linked) inheritance? A. AIDS B. Down syndrome C. Sickle-cell anemia D. Hemophilia

D. Hemophilia

An allele for lactase persistence allows humans to digest milk as adults. People who lack this allele are lactose intolerant in adulthood. What is the pattern of inheritance? A. Lactase persistence is sex-linked recessive. B. Lactase persistence is autosomal recessive. C. Lastase persistence is sex-linked dominant. D. Lactase persistence is autosomal dominant.

D. Lactase persistence is autosomal dominant.

What is a feature of the human genome? A. Plasmids B. Messenger RNA C. Transfer RNA D. Mitochondrial DNA

D. Mitochondrial DNA

The system of sex determination in chimpanzees (Pan troglodytes) is the same as in other mammals. A chimpanzee has 48 chromosomes in the nuclei of its body cells. What can be deduced from this interpretation? A. The sex of the chimpanzee. B. The number of genes in each chromosome. C. Whether non-disjunction has occurred. D. The number of autosomes in a diploid cell.

D. The number of autosomes in a diploid cell.

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. Thyroid cancer

In which situation are alleles exchanged? A. During the separation of sister chromatids. B. In the transmission of linked genes. C. During fertilization when sperm and egg chromosomes pair up. D. When chiasmata are formed between non-sister chromatids.

D. When chiasmata are formed between non-sister chromatids.

When genotype AaBb is crossed with genotype aabb, how many genotype combinations of offspring are possible?

Four

What is the Law of Independent Assortment?

Genes for different traits are inherited independently of each other.

Describe Prophase I.

Homologous chromosomes (maternal and paternal) are replicated and then they join side by side via synapsis , forming a tetrad. This tetrad then splits to opposite cells and one cell gets a paternal while one gets maternal chromosome (each get 2 chomatids). This is also the point where recombination occurs/crossing over between homologous chromosomes (not sister chromatids).

Describe Anaphase I.

Homologs separate and begin moving to opposite sides of cell.

Describe Metaphase I.

Migration of tetrads to metaphase plate is complete (tetrads are lined up at the center).

Compare the processes of mitosis and meiosis. (6 marks)

Possible answers: Mitosis: one cell division & Meiosis: two divisions / reduction division Mitosis: chromosome number does not change & Meiosis: converts diploid to haploid cells Mitosis: products genetically identical & Meiosis: products genetically diverse Mitosis: separation of sister chromatids in anaphase & Meiosis: separation of homologous chromosomes in anaphase I and sister chromatids in anaphase II Mitosis: no crossing over & Meiosis: crossing over in prophase I Mitosis: no formation of tetrads / no synapsis & Meiosis: formation of tetrads / synapsis Mitosis: produce cells for growth/repair/asexual reproduction & Meiosis: produce sexual cells / gametes for sexual reproduction Mitosis: two cells produced & Meiosis: four cells produced Mitosis: daughter cells with both copies of chromosomes/random assortment does not occur & Meiosis: random assortment of maternal/ paternal chromosomes Mitosis: replication of DNA in interphase & Meiosis: replication of DNA in interphase I Mitosis: four phases: prophase, metaphase, anaphase, telophase & Meiosis: same four phases twice

Describe Anaphase II.

Sister chromatids separate and begin moving to opposite sides.

Describe Prophase II.

Spindle apparatus forms. If nuclear envelope formed at the end of meiosis I, it breaks apart. Kinetochore microtubules attach to each sister chromatid.

Why don't linked genes follow Mendel's Law of Independent Assortment?

The linked genes are inherited together and therefore their alleles will not segregate independently during gamete formation.

Describe Telophase I.

The two cells finish cytokinesis and nuclear membranes reform around the chromosomes.