Genetics/Meiosis Review Questions

Question A cross between two pea plants hybird for a single trait produces 60 offspring. Approximately how many of the offspring would be expected to exhibit the recessive trait?

Answer Pp x Pp ¼ pp = recessive trait Answer: 60 offspring x ¼ = 15 offspring would express the recessive trait

Question Compare the final products of mitosis to the final products of meiosis.

Answer Mitosis: 2 diploid (2n) daughter cells that are identical to the original cell Meiosis: 4 haploid (n) gametes (sperm or eggs)

Question Determine the possible genotypes & phenotypes of the children for a couple who's blood types  are homozygous A & heterozygous B.

Answer 50% (2 of 4 squares) are IAIB & those kids would have AB blood. The other 50% (2 of 4 squares) are IAi, those kids will have Type A blood.

Question Explain the difference between diploid and haploid.

Answer Diploid= The state of having each chromosome in two copies per nucleus or cell. Haploid= The state of having one copy of each chromosome per nucleus or cell.

Question In hamsters, black coat is dominant to white coat and rough coat is dominant to smooth coat. If two heterozygous black-rough coated hamsters where mated. What would be the phenotype ratio of the F1 generation?

Answer 9 Black-rough : 3 Black-smooth : 3 White-rough : 1 White-smooth

Question Explain the difference between homologous chromosomes and sister chromatids.

Answer Homologous Chromosomes= A pair of chromosomes made up of two homologs. Homologous chromosomes have corresponding DNA sequences and come from separate parents; one homolog comes from the mother and the other comes from the father. Homologous chromosomes line up and synapse during meiosis. Sister Chromatids= 2 duplicates of a chromosome created by replication.

Question In cats, the allele for black fur is dominant to the allele for brown fur, and the allele for short hair is dominant to the allele for long hair. Homozygous black fur heterozygous short hair male, heterozygous black fur long hair female Give Genotype and Phenotype Ratio

Answer BBSs x Bbss Genotype ratio = 4 BBSs : 4 BBss : 4 BbSs : 4 Bbss Phenotype ratio = 8 Black-short : 8 Black-long

Question In human cells, 2N=46. How many chromosomes would you expect to find in a sperm cell? In an egg cell? In a cell in your brain? Explain your answers.

Answer Sperm cells (haploid = n) = 23 Egg cells (haploid = n) = 23 Brain cells (diploid = 2n) 46

Question If a man with hemophilia (difficulties with blood clotting) marries a homozygous normal woman, what is the probability of them having a hemophiliac child?

Answer Since the mom is not a carrier there is a 0% chance of having a hemophiliac child

Question- 2 part What is crossing over and when does it occur? Which part of meiosis is most like mitosis?

Answer Crossing Over= The exchange of DNA sequences between chromatids of homologous chromosomes during meiosis, occurs in prophase 1. Meiosis 2

Question A test was done to determine the biological father of a child.  The child's blood Type is A and the mother's is B.  Dude #1 has a blood type of O, & dude #2 has blood type AB.  Which dude is the biological father?

Answer It is possible with the mom and Dude #2 to produce the child

Question In tomato plants, the allele for purple stems is dominant to allele for green stems and the allele for red fruit is dominant to the allele for yellow fruit. If two tomato plants heterozygous for both traits are crossed. state what proportion of the offspring would be expected to have purple stems and yellow fruit.

Answer 3/16

Question When a mouse with black fur is crossed with a mouse with white fur, all F1 generation offspring have gray fur. What genotypic and phenotypic ratios be expected in the F2?

Answer Genotype ratio = 1 BB : 2 Bb : 1 bb Phenotype ratio = 1 Black : 2 Gray : 1 White

Question Give the gametes for the following: AaBb

Answer AB, Ab, aB, ab

Question In garden peas, tall vine (T) is dominant and short vine (t) is recessive. If a heterozygous tall pea plant is crossed with a short pea plant, what genotypes and phenotypes are possible in the F1 generation?

Answer Heterozygous tall pea plant = Tt Short pea plant = tt Answer: Genotypes for F1 = Tt and tt Phenotype for F1 = Tall and short

Question Give the genotypic and phenotypic ratio of the potential children of a couple, if the man is heterozygous A-type blood and his wife is heterozygous B-type blood.

Answer Genotype ratio = 1 IAIB : 1 IBi : 1 IAi : 1 ii Phenotype ratio = 1 AB : 1 B : 1 A : 1 O

Question What are the possible blood types of a child who's parents are both heterozygous for "B" blood type?

Answer There is a 75% (3 of 4) chance that the child will be Type B, and a 25% (1 of 4) chance that the child will inherit Type O (ii).

Question In dogs, wirehair is a dominant trait, smooth hair is recessive. Two wire-haired dogs produce a male puppy that is wire-haired. To find out most quickly whether he carries the allele for smooth hair, he should be mated to a specific type of female. What is the name of this senario? (be specific for the term)

Answer He should be mated with a smooth haired (homozygous recessive), this would be a test cross

Question In garden peas, axial flower position is dominant and terminal flower position is recessive; tall vine is dominant and short vine recessive. A plant known to be purebred for tall vine and axial flowers is crossed with a plant having short vines and bearing terminal flowers. What is the genotype of the offspring?

Answer AaTt

Question In cocker spaniels, black is a dominant trait (B), red is recessive (b). Solid color is dominant (S) and white spotting is recessive (s). A red male was mated to a black-and-white female. They had five puppies as follows: 1 black, 1 red, 1 black-and-white, and 2 red-and-white. What are the genotypes of the parents?

Answer Male = bbS? Female = B?ss * need to look at puppies to determine genotypes Since all phenotypes appeared, then the parents must have been heterozygous for the traits Answer: Male = bbSs Female = Bbss

Question What are the chances of a woman with Type AB and a man with Type A having a child with Type O?

Answer 0%, because the woman has blood type AB

Question Optic atrophy (blindness due to degeneration of the optic nerve) occurs as a result of the action of an X-linked recessive gene. A woman with the optic atrophy marries a normal man. What is the expected genotypic and phenotypic ratio of their children?

Answer Woman=XaXa woman with optic atrophy Man= XAY normal man Genotypic Ratio: 2XAXa:2XaY Phenotypic Ratio: 2 female carriers: 2 males with optic atrophy

Question In cattle, hair color shows codominance. Red is dominant, and white is recessive. In the heterozygous condition codominance is shown as roan (something of a light red) coat color. If a roan bull and a roan cow are mated over several years and produce 12 offspring. How many of the offspring would be expected to be white? Roan?

Answer RWxRW 3 red:6 roan:3 white

Question In flies, white eyes are an X-linked recessive trait. Cross a carrier female with a red-eyed male fly. What % of the children would have white eyes? What % of the girls would be carriers? What percent of all the kids would be carriers?

Answer Female=XRXr Male=XRY 25% white eyed offspring 50% of girls would be carriers 25% of all kids would be carriers

Question Polyploid organisms results from: (a) crossing over (b) non disjunction (c) mitosis (d) random assortment