REVIEW 4: HEREDITY & MOLECULAR GENETICS UNIT

point mutation

Base substitution occurs when one base is switched out with another base, Frameshift mutation occurs when one base is added or removed (deletion, insertion)

inducible operon (digestive pathway = lac operon)

a specific small molecule that binds to a bacterial regulatory protein and changes its shape so that it cannot bind to an operator, thus switching an operon on lactose absent, repressor active, operon off (blocks RNA polymerase from binding to operator) lactose present, repressor inactive, operon on (RNA polymerase binds to operator)

1. 2005:2 The unit of genetic organization in all living organisms is the chromosome. a. Describe the structure and function of the parts of a eukaryotic chromosome. You may wish to include a diagram as part of your description. b. Describe the adaptive (evolutionary) significance of organizing genes into chromosomes. c. How does the function and structure of the chromosome differ in prokaryotes?

a. Chromatid structure: comprised of histones and DNA Chromatid function: efficiently package DNA into a small volume to fit into the nucleus of a cell and protect the DNA structure and sequence. Centromere structure: noncoding/ uncoiled/ narrow Centromere function: joins/ holds/ attaches chromatids together Nucleosome Structure: Histones, DNA wrapped around special proteins Nucleosome Function: Packaging/ compacting Genes or DNA structure: brief DNA description Genes or DNA function: codes for proteins or for RNA Telomeres structure: noncoding repetitive sequences Telomeres function: protection against degradation/ aging, limits number of cell division b. Allows for Genetic Variation through independent assortment and crossing over • Allows for Genetic Stability through efficiency of transfer of genetic information, prevents loss of genetic information, offspring get same number of chromosomes, linked genes tend to be inherited together • Allows for Gene Regulation through increased complex structure, histone acetylating and methylation • Allows for Complexity because it allows for more genes and the evolution of new genes can occur/transposons • Allows for Diploid/Polyploid through genetic fitness, minimizes the effect of harmful alleles/ backup copy, extra set(s) of alleles cEukaryotic Chromosome • Found in nucleus • Linear chromosomes • Many chromosomes. • Made of chromatin, a nucleoprotein (DNA coiled around histone proteins). • Copies chromosomes, then the cell grows (G2 phase), then goes through mitosis to organise chromosomes in two equal groups. Prokaryotic Chromosome • Found in cytoplasm. • Circular chromosome attached to the inside of the cell membrane. • Single chromosome plus plasmids. • Made only of DNA. • Copies its chromosome and divides immediately afterwards

In peas the trait for tall plants (T) is dominant and the trait for short plants (t) is recessive. The trait for yellow seed color is dominant (Y) and the trait for green seed color is recessive (y). A cross between two plants results in 296 tall yellow plants and 104 tall green plants. Which of the following are most likely to be the genotypes of the parents? (1999:28) a. TTYY x TTYY b. Ttyy x TTYy c. TtYy x TtYy d. TtYy x TTYy e. TtYY x Ttyy

d

These two questions refer to the birth of a child with blood type A to a mother with blood type B. (1999:102-103) 8. The father must have which of the following blood types? a. AB only b. Either AB or B c. Either AB or O d. Either AB or A e. AB or A or O

d

In humans, red-green color blindness is a sex-linked recessive trait. If a man and a woman produce a color-blind son, which of the following must be true? (1999:43) a. The father is color-blind. b. Both parents carry the allele for color blindness. c. Neither parent carries the allele for color blindness. d. The father carries the allele for color blindness. e. The mother carries the allele for color blindness.

e

phenotype vs. genotype

phenotype - observable traits genotype - genes it carries

Meiosis produces

produces haploid gametes

operons

prokaryotes • cluster of genes for enzymes in a pathway • controlled by repressor protein`

repressible operon (synthesis pathway = tryp operon)

protein that inhibits gene transcription -In prokaryotes, this protein binds to the DNA in or near the promoter. when bound to operator, no production of tryptophan -too much tryptophan present, bounds to repressible operon, which then binds to operator

transcription factors

proteins which enable bonding of RNA polymerase to gene

Meiosis 1

separates homologous pairs: reduction division crossing over in Prophase 1

Meiosis 2

separates sister chromatids: produces 4 sex cells

Law of Segregation

states that allele pairs separate or segregate during gamete formation, and randomly unite at fertilization.

DNA

ACTG nitrogen bases, double helix • A:T,C:G

RNA

ACUG nitrogen bases, single helix

Central Dogma

DNA - RNA - protein - trait

transcription

DNA - mRNA in nucleus • RNA polymerase copies coding strand & produces mRNA

alleles

Different versions of same gene

Which of the following best describes the parents in a testcross? (1999:9) a. One individual has the dominant phenotype and the other has the recessive phenotype. b. Both individuals are heterozygous. c. Both individuals have the dominant phenotype. d. Both individuals have the recessive phenotype. e. Both individuals have an unknown phenotype.

a

Meiosis reduces chromosome number and rearranges genetic information. a. Explain how the reduction and rearrangement are accomplished in meiosis . b. Several human disorders occur as a result of defects in the meiotic process. Identify ONE such chromosomal abnormality; what effects does it have on the phenotype of people with that disorder? Describe how this abnormality could result from a defect in meiosis. c. Production of offspring by parthenogenesis or cloning bypasses the typical meiotic process. Describe either parthenogenesis or cloning and compare the genomes of the offspring with those of the parents.

a. Reduction - homologous chromosomes pair, then separate and move to opposite poles during 1st meiotic division, chromatids separate during 2nd meiotic division. Rearrangement - Crossing over when two chromosomes of a homologous pair exchange equal segments with each other. , random alignment (independent assortment) of tetrads b. Turner syndrome, women's sex organs are sterile, they have a webbed neck, low-set ears, and a short stature. It is a form of nondisjuntion and happens when the sex chromosomes (XX, XY) do not divide properly. c. Cloning - using a somatic cell or cells from a multicellular organism to make on or more genetically identical individuals. An example would be when bacteria reproduce asexually. The genomes of offspring and parents are identical.

A form of vitamin D-resistant rickets, known as hypophosphatemia, is inherited as an X- linked dominant trait. If a male with hypophosphatemia marries a normal female, which of the following predictions concerning their potential progeny would be true? (1990:44) a. All of their sons would inherit the disease b. All of their daughters would inherit the disease c. About 50% of their sons would inherit the disease d. About 50% of their daughters would inherit the disease e. None of their daughters would inherit the disease

b

A represents the dominant allele and a represents the recessive allele of a pair. If, in 1000 offspring, 500 are aa and 500 are of some other genotype, which of the following are most probably the genotypes of the parents? (1990:4) a. Aa and Aa b. Aa and aa c. AA and Aa d. AA and aa e. aa and aa

b

These two questions refer to the birth of a child with blood type A to a mother with blood type B. If the father has blood type AB, which of the following statements is correct about the mother? a. She contributes an I B allele, which is recessive to the father's IA allele. b. She contributes an i allele, which is recessive to the father's IA allele. c. She contributes an I B allele, which is codominant to the father's I Aallele. d. She contributes an i allele, which is codominant to the father's I B allele. e. She is homozygous for the I B allele

b

co-dominance

ex: blood type genetic scenario where neither allele is dominant or recessive and both get expressed

epistasis

ex: coat color There is that one gene or allele masking the phenotypic expression of the other genes or alleles in the interaction

pleiotropy

ex: dwarfism/gigantism occurs when one gene will code and control the phenotype or expression of several different and unrelated traits.

incomplete dominance

ex: pink flower intermediate inheritance in which one allele for a specific trait is not completely expressed over its paired allele. This results in a third phenotype in which the expressed physical trait is a combination of the phenotypes of both alleles

polygenic

ex: skin color, height are controlled by two or more than two genes (usually by many different genes) at different loci on different chromosomes

Mutations

fuel for evolution = variation, genetic change

translation

mRNA - protein • in cytoplasm • codons on mRNA read by ribosome • matched to anticodons of tRNA • tRNA carries amino acids to mRNA & ribosome assembles polypeptide chain • start codon (Met) & stop codons, redundancy in code • universal code (single common ancestor)

insertion

the addition of one or more nucleotide base pairs into a DNA sequence

Law of Independent Assortment

when two or more characteristics are inherited, individual hereditary factors assort independently during gamete production, giving different traits an equal opportunity of occurring together

deletion

which a part of a chromosome or a sequence of DNA is lost during DNA replication