On which of the following phases does nondisjunction occur?
Nondisjunction may result in the production of daughter cells that have either too many or too few chromosomes. The abnormal number of chromosomes can lead to various genetic disorders such as trisomy-21 and Klinefelter syndrome. Which of the following happens during nondisjunction that results in the unequal distribution of chromosomes in the daughter cells?
Independent assortment happens when homologous chromosomes are independently and randomly aligned during Metaphase I. This process results in a number of possible genetic combinations. What formula can we use to determine the total number of combinations?
The following are the factors that can cause triploidy in humans except:
Genetic recombination is the result of the crossing over of genes. However, for mitochondrial DNA, recombination does not happen. This implies that:
One source of genetic variation during meiosis is when pairs of homologous chromosomes exchange their genetic material in a process called:
What could be causing the large differences in various traits between you and your sibling?
Non-disjunction during meiosis I and meiosis II results in ______ cells.
How many combinations of maternal and paternal chromosomes are possible for gametes produced by a diploid organism with 2n=20? Also what are the chances that a gamete produced by this organism will only have maternal chromosomes?
Which of the following statements about crossing over is incorrect?
How do genes that are far apart on the same chromosome assort independently?
Assume that we are trying to map four genes in a chromosome. Given the following recombination frequencies, what will be the sequence of the genes in the chromosome?
A-B = 25%
B-C = 15%
A-D = 15%
B-D = 40%
Two genes of a flower are linked and are 20 map units apart. One gene controls height (T = tall vs. t = dwarf) and the other controls the flower colour (P = purple vs. p = white). Crossing homozygous tall plant with white flower with a homozygous dwarf plant with purple flower and the resulting F1 progeny is crossed with homozygous dwarf plants with white flowers. If the F2 progeny has 100 plants, which of the following correctly shows the number of plants of each four phenotypes?
Genes for eye colour and wing size of Drosophila are located on the same chromosome. A wild-type Drosophila heterozygous for both eye colour and wing size is mated with a Drosophila which is homozygyous recessive at both the loci. Which of the following accurately depicts the percentage of offsprings with recombinant phenotypes?
To determine the order of body colour, wing size and eye colour genes on the chromosome of Drosophila, which of the following sets of crosses will you perform?
a. Cross 1 - ♂ wild-type heterozygous for normal wings and red eyes x ♀ recessive homozygous for vestigial wings and purple eyes. Cross 2 - ♂ wild-type heterozygous for gray body and red eyes x ♀ recessive homozygous for black body and purple eyes.
b. Cross 1 - ♂ wild-type homozygous for normal wings and red eyes x ♀ recessive homozygous for vestigial wings and purple eyes. Cross 2 - ♂ wild-type homozygous for gray body and red eyes x ♀ recessive homozygous for black body and purple eyes.
c. Cross 1 - ♂ wild-type heterozygous for normal wings and red eyes x ♀ recessive homozygous for vestigial wings and purple eyes. Cross 2 - ♂ wild-type homozygous for gray body and red eyes x ♀ recessive homozygous for black body and purple eyes.
d. Cross 1 - ♂ recessive homozygous for vestigial wings and purple eyes x ♀ recessive homozygous for vestigial wings and purple eyes. Cross 2 - ♂ recessive homozygous for black body and purple eyes x ♀ recessive homozygous for black body and purple eyes.
The recombinant frequencies of three different crosses involving two genes at a time are as follows:
Between B and W = 12%
Between T and W = 5%
Between B and T = 18%
Choose the correct order of the three linked genes.
In a hypothetical organism, coat colour, wings and height are inherited in the same way that they are in humans. The two alleles for coat colour of the organism are: B = brown, b = white; for its wings are: W = normal wings, w = vestigial, and for its height are: T = tall, t = dwarf. A researcher carried out two types of breeding experiments (BE) in the laboratory and obtained the following results.
What is the recombination frequencies for BE1 and BE2?
A wild-type Drosophila which is heterozygous for gray body and normal wings is mated with a Drosophila with black body and vestigial wings. The phenotypic distribution of the offspring is as follows: wild-type - 1556, black with vestigial wings - 1570, gray with vestigial wings - 324, black with normal wings - 316. What will be the recombination frequency between the genes for body colour and wing size?