Exam 1 Concepts
What is the type of cell division involved in the healing of wounds?
mitosis
Drosophila sperm cell contain four chromosomes. In total, how many chromatids would be present at metaphase I of meiosis?
16
Two of the genes studied by Mendel, a gene controlling seed color (yellow vs. green), and a gene controlling flower color (purple vs. white), are both located on the same chromosome in peas, 60 cM apart. Mendel performed dihybrid crosses involving these two genes, yet he reported the traits of seed and flower color as assorting independently. How can this be?
Mosquitoes heterozygous for three recessive mutations, v, w and z were test-crossed to mosquitoes homozygous recessive for all three genes. The results of this cross are given below. An upper case letter indicates a mutant phenotype, and a +i ndicates the wild-type phenotype.
Phenotypes Number
V W Z 1
V + + 61
+ W + 88
V + Z 96
+ + Z 367
+ + + 3
+ W Z 46
V W + 338
Which of the following is the correct order of these genes on the chromosome?
V Z W
Which structures separate during metaphase I of meiosis?
homologous chromosomes
at least 2
What were the isotopes used by Hershey and Chase in their experiments and what was each of their functions?
32P: used to label the DNA because phosphorous was present only in DNA and not proteins
35S: used to label proteins
Achondroplastic dwarfism is an inherited condition. In one study, 108 achondroplastic dwarfs produced 27 offspring, while 457 non-dwarf individuals produced 582 children. What is the relative fitness of the achondroplastic dwarf genotype?
0.25/1.27 = 0.196
The I gene involved in ABO blood type encodes an enzyme that modifies the polysaccharide chains found on cellular glycoproteins. In a sperm cell of a man of blood type BB, a mutation occurs causing an amorphic allele of the I gene. This sperm cell carrying the mutant allele fertilizes one of his wife's eggs. His wife's blood type is O. What is the child's blood type?
blood type O
Consider the cross aaBbccDDEe x AaBbCcDdEe.
What proportion of offspring will have genotype A_B_C_D_E_?
9/64
Most RNA viruses have single-stranded RNA genomes, but some, like bluetongue virus, have double-stranded RNA genomes. Of the viruses below, which one must be bluetongue virus and why?
# of nucleotides:
Virus #1: 32-A; 18-U; 18-G; 32-C; 0-T
Virus #2: 25-A; 25-U; 33-G; 17-C; 0-T
Virus #3: 28-A; 28-U; 22-G; 22-C; 0-T
Virus #4: 22-A; 0-U; 28-G; 28-C; 22-T
Virus #5: 36-A; 18-U; 28-G; 18-C; 0-T
Virus #3: The sum of pyrimidines is equal to the sum of purines. The number of adenosine residues equals to the number of uracil residues and the number of guanosine residues is equal to the number of cytidine residues.
If one strand of a molecule of double-stranded DNA has the sequence 5'-GTCATA-3', what is the sequence of the other strand, reading 5' to 3'?
5'-TATGAC-3'
What is the theory of particulate inheritance?
Theory of particulate inheritance states that when gametes fused during fertilization, the hereditary determinants do not fuse and blend irrevocably; rather, they remain separate and intact.
In Drosophila, the genes for wing size (v+=large, v=vestigial) and bristle length (b+=long, b=short) assort independently, with simple dominance. The following results were obtained from a cross:
302 large, long
98 large, short
297 vestigial, long
101 vestigial, short
What were the genotypes of the parents?
v+v, b+b × v+v, bb
What is the "Philadelphia chromosome"?
a chromosome translocation resulting in a fusion of two genes that causes cancer
In population of 1000 longhorn beetles, 490 have antennae that are divided, which is the characteristic of the homozygous recessive genotype (dd).
A beetle from this population that has the non-divided antennae phenotype (D_) is crossed with a beetle with divided antennae. What is the chance that a beetle resulting from this cross will have divided antennae?
0.21,
The allelic frequency of d is √(490/1000= √0.490= 0.7
Allelic frequency of D is 1-d= 1-0.7= 0.3
Frequency of dd is 0.3)^2= 0.09
The frequency of DD or Dd genotype is 1-dd= 1-0.09=0.91
The probability of Dd parent is = 2×0.3×0.7=0.42
The probability of dd parent is 1 because it is already given in the question.
D- × dd
The DD genotype bearing parent produces only non divided antena.
The Dd genotype bearing parent produces half divided and half non divided antenna.
Probability = Dd × dd × offspring. (0.42) × (1) × (0.5) = 0.21
Hemophilia is an example of a recessive X-linked mutation. A woman has a child with hemophilia. Her husband does not have hemophilia, and none of her four grandparents have hemophilia. From which of her four grandparents did the woman inherit the hemophilia allele? Explain your reasoning.
maternal grandmother
Mexican hairless dogs have little hair and few teeth. When Mexican hairless dogs are crossed with normal dogs, about half of the offspring are normal, and half are hairless. From a series of crosses of Mexican hairless x Mexican hairless, there were 132 hairless and 68 normal dogs among the offspring. True-breeding hairless dogs have not been found. For the results of this second cross, is a chi2 test consistent with a 3:1 ratio of hairless:normal dogs?
chi2=8.64, results not consistent
What are new alleles causing color blindness most often caused by?
unequal crossing-over in a linked family of photoreceptor genes I on the X-chromosome
Genes A, B, and C are linked as shown below:
A--------C-----------B
10 cM 15 cM
These three genes control steps in a biochemical pathway for pigment synthesis as follows:
A------------B-----------C
white----->yellow---->brown---->black
What proportion of the offspring of the test cross A C b/a c B x a c b/a c b, would be yellow?
Yellow = 0.3825+0.0075 = 0.39 = 39%