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The fact that all seven of the garden pea traits studied by Mendel obeyed the principle of independent assortment means that:
All seven pairs of alleles determining these traits behave as if they are on different chromosomes.
How did Mendel come to conclusions that led to the principle of segregation that says that alleles separate so that each egg or sperm cell received only one of them?
Analysis of monohybrid crosses
The enzyme that connects okazaki fragments on the lagging strand is _______________. Helicase DNA polymerase DNA ligase Topoisomerase
DNA ligase
Cancer is caused by cells reproducing uncontrollably. There are three checkpoints during the cell cycle to ensure that cells reproduce only when they should. Errors in DNA replication would stop a cell moving from _
G2 to Mitosis
A sexually reproducing organism has two genes located on different chromosomes, one for head shape (H) and one for tail length (T). Its genotype is HhTt. Which of the following are possible allele combinations in this organism's gametes? Select all that apply.
HT hT
Gametes created through the process of meiosis have __________ the number of chromosomes as the parent cell.
Half
Albinism (lack of skin pigmentation) is caused by a recessive autosomal allele. A man and a woman, both normally pigmented, have an albino child together. For this trait, what is the genotype of the albino child?
Homozygous recessive
A sexually reproducing animal has two unlinked genes, one for body length (L) and one for fur color (F). Its genotype is LlFf. Which of the following genotypes is possible in a gamete from this organism?
Lf
What are homologous chromosomes?
Chromosomes that are similar is their size, shape, and gene content
Events during meiosis lead to genetic variation. What important event happens during prophase I?
Crossing over
Shell color in clams is thought to be controlled by three different genes (each with two alleles). Shell coloration runs a range between pure white and dark purple. The addition of dominant alleles makes the shells more purple in coloration, while the addition of recessive alleles makes the shells more white. The majority of clams have shells that are medium purple, whereas the other colors are present, but in fewer numbers. This is an example of:
Quantitative trait
When does DNA replication occur during the cell cycle?
S phase
Two plants are crossed, resulting in offspring with a 3:1 phenotype ratio for a particular trait. This indicates:
That the parents were both heterozygous.
Genotype
The combination of alleles that an organism inherits.
Phenotype
The outward appearance of an organism based on inherited DNA sequence
Centromeres uncouple and chromatids are separated from each other.
The statement is true for mitosis and meiosis II.
When a cell divides, two nuclei that are genetically identical are formed.
The statement is true for mitosis only.
Which statement about the daughter cells following mitosis and cytokinesis is correct? They are genetically different from each other and from the parent cell They are genetically identical to each other and to the parent cell They are genetically identical to each other but different from the parent cell Only one of the two daughter cells is genetically identical to the parent cell
They are genetically identical to each other and to the parent cell
True or False. In genetics, a "test cross" is used to determine the genotype of one of the members of the parental cross.
True
True or False: A test cross can indicate whether an individual of a dominant phenotype is homozygous or heterozygous.
True
After the S phase, what comprises a single chromosome?
Two sister chromatids
Cytokinesis usually, but not always, follows mitosis. If a cell completed mitosis but not cytokinesis, what would be the result?
a cell with two nuclei
A man who carries an X-linked allele will pass it on to ______________.
all of his daughters.
The centromere is a region in which __________.
chromatids are attached to one another.
Recombinant chromosomes (chromosomes with new combinations of genetic material) are the result of __________.
crossing-over
After telophase I of meiosis, what is the chromosomal makeup of each daughter cell?
haploid, and the chromosomes are composed of two chromatids
What kind of chemical bond holds together the sugar-phosphate backbones of DNA?
hydrogen
In contrast to animals, which are almost always diploid, many plants are polyploid. In fact, strawberries are octaploid, meaning ________.
or each different chromosome, there are eight versions or homologs
The frequency of crossing over between any two linked genes is ___________________.
proportional to the distance between them on the chromosome.
True or False: In eukaryotes, the enzyme telomerase prevents shortening of chromosomes during replication.
t
Taxol is an anticancer drug extracted from the Pacific yew tree. In animal cells, taxol disrupts microtubule formation by binding to microtubules and accelerating their assembly from the protein precursor, tubulin. Surprisingly, this stops mitosis. Specifically, taxol must affect __________. (Hint: Read through this question. You do not need to have any previous knowledge of taxol to answer this question.)
the fibers of the mitotic spindle.
When genes are closely linked, which of Mendel's findings is not in action when predicting the results of crosses involving such genes?
the law of independent assortment
What proportion of chromosomes in a skin cell are paternal (i.e. from the father) chromosomes?
½
Genes on the same chromosome can be linked. However, they are sometimes separated through crossing over during meiosis I. The distance between genes on a chromosome determines the frequency of crossing over. Scientists can map the locations of genes on a chromosome by doing test crosses, examining the number of offspring that have the parental genotypes/phenotypes and those that have recombinant (not-parental) genotypes/phenotypes, and calculating recombination frequencies. Genes on the same chromosome can be linked. However, they are sometimes separated through crossing over during meiosis I. The distance between genes on a chromosome determines the frequency of crossing over. Scientists can map the locations of genes on a chromosome by doing test crosses, examining the number of offspring that have the parental genotypes/phenotypes and those that have recombinant (not-parental) genotypes/phenotypes, and calculating recombination frequencies. When a test cross was performed between lz+ lz d+ d and lz lz d d parents, the following results were found in the offspring. Offspring genotypes and numbers of individuals: lz+ lz d+ d 462 lz lz d d 459 lz+ lz d d 38 lz lz d+ d 41
(38 + 41)/1000 *100 = 7.9%
Black fur in mice (B) is dominant to brown fur (b). Short tails (T) is dominant to long tails (t). What fraction of the progeny of the cross BbTt þ BBtt will have black fur and short tails?
1/2
If the liver cells of an animal have 24 chromosomes, its sperm cells would have how many chromosomes?
12
Albinism (lack of skin pigmentation) is caused by a recessive autosomal allele. A man and a woman, both normally pigmented, have an albino child together. The couple decides to have a second child. What is the chance that this child will be albino?
25%
A dihybrid cross is performed between plants that differ in two Mendelian traits: Stem length (T or t) and flower coloration (P or p). Tall stems are dominant to short stems and purple flowers are dominant to white flowers. If both parents are heterozygous for both traits, how many offspring (what fraction) are expected to have tall stems and white flowers?
3/16
Dogs have 78 chromosomes in their diploid cells. If a diploid dog cell enters meiosis, how many chromosomes and chromatids will be present in each daughter cell at the end of meiosis I?
39 chromosomes and 78 chromatids
How many unique gametes could be produced through independent assortment by an individual with the genotype AaBbCCDD?
4
When crossing over occurs, the result is:
4 chromosomes: 2 nonrecombinant and 2 recombinant
