Project #15317 - Genetics

.   When requested, neatly present your calculations on an attached sheet or on the blank side of a page in order to receive points.   Understand how you arrive at (ie., calculate) the answers as you will be expected to do so on exams.

                  

1.  (3 pts.).  In mice, females are XX (ie., 2 X chromosomes) and males are XY.  Locus 1: allele E = ears;  e = no ears. Locus 2: allele B = black hair; b = white.  Upper case letter is dominant. Previous research determined that the locus 2 was part of an X chromosome and locus 1 was part of an autosome. Parents & phenotypes: Males =  ears & black; Females = no ears & white. Both parents are true-breeding.  The parents mate to produce the F1 generation.  The F1-generation mice mate to produce the F2 of 400 mice.

_________: the expected number of F2-generation mice with white fur.

_________: the expected number of F2-generation male mice with white fur.

_________: the expected number of F2-generation female mice with ears and black fur.

2. (2 pts ).  Traits:  tails & hair color in mice. Female are XX (ie., 2 X chromosomes), males are XY. Locus 1: allele T = tails;  t = no tails.  Locus 2: allele B = black hair; b = white.  Upper case letter is dominant. Parents & phenotypes: Males = no tails & white; Females = tails & black; both sexes are true-breeding. F1 phenotypes:  All tails & black; 50% male, 50% female. Parents mate & produce F1. The F1 mice mate to produce the F2 generation of 800 mice, as per the table:

 ______: Which gene locus, tail or hair, is sex-linked (ie., on the X chromosome)?

(sex)______& (locus) _________: Which sex, male or female, is hemizygous for which gene locus?

# F2 generation mice

Sex

Hair

Tails

300

Female

Black

Yes

100

Female

Black

No

150

Male

Black

Yes

150

Male

White

Yes

50

Male

Black

No

50

Male

White

No

 

3. (4 pts). A diploid somatic cell of a hypothetical eukaryote contains two pairs of homologs in its nucleus (2N = 4).  One pair of homologs is metacentric and the other pair is telocentric.  The metacentric pair is heterozygous at two gene loci and each locus is on a different arm.  At one locus, the alleles are identified by the letters “A” and “a”.  At the other locus, the alleles are identified by the letters “B” and “b”.  The upper case letter indicates the dominant allele and the lower case indicates the recessive allele at each locus.  The dominant alleles of the two gene loci are on one of the metacentric homologs and the recessive alleles are on the other metacentric homolog.  The telocentric homologs are heterozygous for two loci on the long arm.  The locus closest to the centromere has alleles symbolized by the letters “E” and “e” while the other locus on the telocentric homologs has alleles represented by the letters “H” and “h” .  The dominant alleles of those 2 loci are on one of the telocentric chromosomes while the recessive alleles are on the other homolog. 

For the stage of the cell cycle listed below, please draw and label the chromosomes as instructed below and using the allele symbols. Use a vertical line to represent each double-stranded DNA molecule and an open circle,   , to indicate the site of the centromere.  Clearly label the positions of the centromeres, telomeres, each gene locus and the allele at each gene locus on each chromosome and chromatid.  Please do not draw other structures such as the nuclear envelope, spindle fibers etc.   Pretend that the chromosomes are sufficiently condensed so that they could be observed as distinct chromosomes. The stage of the cell cycle is:  prophase of mitosis.  Neatly illustrate and label your chromosomes in the box:

 

 

 

 

 

 

 

4. (4 points).  The mouse (Mus musculus), a diploid, is 2N = 40 with a C-value of 2.8 billion base pairs.

 _____: How many nuclear chromosomes in a cell at prophase I?

 _____: How many chromosomes in the cell at the end of telophase I prior to cytokinesis?

_____: How many sex chromosomes are in a cell at metaphase II?

 _______________: How many base pairs of DNA are expected in a cell at anaphase II?

5. (2 pts). The probability of a specific combination of offspring =   { n! / (w! x!)} multiplied by pw multiplied by   q x. Where n, w and x refer to numbers of observations (e.g. progeny) and p and q refer to the probability of the respective observation.

 A man and a woman are heterozygous for cystic fibrosis, an autosomal recessive disorder: ie., both are carriers (genotype Aa).

_______: (2 pts) what is the probability that, if they have 4 children by separate conceptions and births, 2 will have CF and 2 will be normal? Show your work.

6.(5 pts.).  In mice, females are XX (ie., 2 X chromosomes) and males are XY.  Locus 1: allele E = ears;  e = no ears. Locus 2: allele B = black hair; b = white.  Upper case letter is dominant. Previous research determined that the locus 2 was part of an X chromosome and locus 1 was part of an autosome. Parents & phenotypes: this is a reciprocal cross relative to the genotypes and phenotypes described in question 1. Both parents are true-breeding.  The parents mate to produce the F1 generation.  The F1-generation mice mate to produce the F2 of 400 mice.

__________________________________: the genotype and phenotype of the female parent used to make this reciprocal cross.

__________________________________: the genotype and phenotype of the male parent used to make this reciprocal cross.

_________: the expected number of F2-generation mice with white fur.

_________: the expected number of F2-generation male mice with white fur.

_________: the expected number of F2-generation female mice with ears and black fur.

 

 

 

Subject Science
Due By (Pacific Time) 10/31/2013 09:00 am
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