CH13 Mastering Bio

(animation) This animation illustrates ______ as it occurs during ______.

crossing over... prophase 1

When can nondisjunction occur?

--In mitosis, when sister chromatids fail to separate --In meiosis, when sister chromatids fail to separate --In meiosis, when homologous chromosomes fail to separate

According to Figure 13.13, the chances that a woman who is age 45 will have a child with Down syndrome is somewhere around

1 in 30

If a cell has 24 chromosomes, how many chromosomes would each of its four daughter cells have after meiosis?

12

Predict how many genetically different offspring could be produced by outcrossing two 2n=4 individuals (just account for independent assortment and not crossing over).

16 genetically unique offspring, Each parent has the potential to produce 4 genetically unique gametes via independent assortment. When you multiple this potential for each parent, 4 x 4, you get the potential to produce 16 genetically unique offspring.

In human gamete production there is an average of _______ crossover events per chromosome pair

2-3

What is the ploidy of organisms that have two sets of chromosomes?

2n

Dogs have 78 chromosomes in their diploid cells. If a diploid dog cell enters meiosis, how many chromosomes and double-helical molecules of DNA will be present in each daughter cell at the end of meiosis I?

39 chromosomes and 78 double-helical DNA molecules

If a diploid cell undergoes meiosis and produces two gametes with n + 1 chromosomes and two gametes with n− 1 chromosomes, what type of error occurred?

A nondisjunction error occurred in meiosis I, in which both members of a homologous pair migrated to the same pole of the cell.

If a diploid cell undergoes meiosis and produces two gametes that are normal, and one with n − 1 chromosomes, and one with n + 1 chromosomes, what type of error occurred?

A nondisjunction error occurred in meiosis II, in which both sister chromatids of a chromosome migrated to the same pole of the cell.

What kind of cell results when a diploid and a haploid gamete fuse during fertilization.

A triploid cell

A radiation accident leads to a damaged gene in a fruit fly, which leads to improper function of that gene. If this species reproduces asexually, which offspring will inherit a copy of the damaged gene?

All of the offspring

Every few years a giant axe chops off the head of every person who is over 6 feet tall. How will this affect the human population?

Alleles that promote "tallness" will decrease in frequency.

What is a nondisjunction?

An error in cell division that causes homologous chromosomes or sister chromatids to move to the same side of the dividing cell

(animation) which of these gametes contain one or more recombianant chromosomes

B, C, F, and G

What information cannot be obtained from an individual's karyotype?

CANNOT: The sequence of bases of a particular gene CAN: The types of chrom. present in the individual, The ploidy of the individual, The number of autosomes in the individual

Which structure is directly correlated with the production of genetic variability in the daughter cells produced during meiosis?

Chiasma

Which statement best explains why meiosis will be problematic in a triploid (3n) organism? See Section 13.1

Chromosomes will not align properly in meiosis 1

T/F: A haploid organism has one pair of homologous chromosomes.

False, A haploid organism only has one set of chromosomes, so it has no homologous chromosomes.

Explain the relationship between homologous chromosomes and the relationship between sister chromatids. How are these relationships different from one another?

Homologous chromosomes are similar in size and shape, they have the same genes and originate from different parents. Sister chromatids are found in replicated chromosomes and contain exact copies of the single double-helical molecule of DNA.

Which statement about the difference between homologous chromosomes and sister chromatids is correct? --Homologous chromosomes and sister chromatids contain the same genes and the same alleles. --Homologous chromosomes contain the same genes, but may contain different alleles. Sister chromatids contain the same genes and the same alleles. --Sister chromatids contain the same genes, but different alleles. Homologous chromosomes contain the same genes and the same alleles. --Neither homologous chromosomes nor sister chromatids contain the same alleles.

Homologous chromosomes contain the same genes, but may contain different alleles. Sister chromatids contain the same genes and the same alleles.

Meiotic nondisjunction could be a result of

Incorrect incorrect segregation of homologous chromosomes during meiosis I.

Which of the following statements about meiosis and mitosis is true? --In meiosis II and mitosis, a diploid cell divides. --Meiosis II is similar to mitosis in that sister chromatids of each chromosome separate. --In mitosis and meiosis I, homologous chromosomes move independently of each other. --Each daughter cell produced during meiosis and mitosis is genetically identical to the parent cell.

Meiosis II is similar to mitosis in that sister chromatids of each chromosome separate.

Homologous pairs of chromosomes are lined up independently of other such pairs during _______

Metaphase 1

What is the composition of a tetrad at the beginning of prophase 1?

One pair of homologous chromosomes

All of the following processes produce genetic variation among offspring EXCEPT

Segregation of sister chromatids during meiosis 2

A particular plant species can reproduce both sexually and asexually. When samples of this plant are grown in an environment where a harmful bacterial pathogen is abundant, the plants that survive are likely to have been produced primarily through what type of reproduction?

Sexual

In analyzing the events of meiosis for answers to why older women produce more aneuploid eggs, biologists have hypothesized that binding between sister chromatids becomes weaker in oocytes of older women. If so, does it lead to problems in chromosome segregation that cause aneuploid conditions such as Down syndrome?

The results are consistent with the hypothesis because they show that as females age, the amount of cohesin falls, the separation between kinetochores increases, and the percentage of aneuploid eggs goes up.

Of the following chromosomal abnormalities, which type is most likely to be viable in humans?

Trisomy ,Some trisomies are viable in humans, but they result in developmental abnormalities, such as Down syndrome (trisomy 21). Only humans with trisomies of the small chromosomes (13, 18, or 21) or the sex chromosomes survive past birth.

Which syndrome is characterized by the XO chromosome abnormality?

Turner syndrome

Homozygous genotype:

When both of the alleles of a given gene pair are the same, the individual is homozygous for that gene. (AA)

If you followed a woman's cells through meiosis, at what stage of meiosis would the amount of DNA in one of these cells be equal to the amount of DNA in one of her G1 phase (before DNA replication) kidney cells?

at the end of meiosis 1

The ease with which humans travel across the globe is likely to increase _______

gene flow

All the genes in a population are that population's

gene pool

Modern travel along with migration reduces the probability of _____ having an effect on the evolution of humans.

genetic drift

Crossing over, resulting in an increase in genetic variation occurs between _______

nonsister chromatids of homologous chromosomes

Genetic drift is a process based on ______

the role of chance

A mutation occurs when _______

there is a change in the DNA sequence of a gene