BIOL189 Chapter 9 Pre-Lecture

Consider one chromosome that contains alleles, A, B, and C, and the homologous chromosome that contains the alleles a, b, and c. If crossing over occurred once during meiosis at a site on the chromosomes between the B gene and the C gene, then what alleles could a resulting chromatid contain?

- A, B, c (if a chromatid containing alleles, A, B, and C crossed over with a chromatid containing alleles a, b, and c at a site between the B genes and the C gene, then one resulting chromatid would contain A, B, and c and the other resulting chromatid would contain a, b, c) - a, b, c

Select all of the following that occur in prophase I of meiosis.

- Spindle forms from microtubules - Chromosomes condense - Nuclear envelope breaks up - Crossing over occurs

Select all of the following that described meiosis.

- cell division needed to produce gametes, or sex cells - divides eukaryotic chromosomes of one cell into four daughter cells that contain half as many chromosomes as the parent cell.

Select all the possible results of nondisjunction in sex chromosomes?

- gamete contains an extra X - XXX zygote - gamete contains an extra Y - gamete is missing a sex chromosome

Select all of the following that are true about meiosis.

- includes two cell divisions - produces gametes with half the number of chromosomes as compared to somatic cells - creates four haploid cells from one diploid cell

Select all of the following organisms that commonly survive as polyploids, which are organisms that have one or more complete sets of extra chromosomes.

- many crop plants - some flowering plants - durum wheat (Durum wheat is tetraploid, which is a type of polyploidy in which there are four sets of chromosomes.)

Select all of the following that are features of both mitosis and meiosis.

- preceded by interphase - prophase, metaphase, anaphase, and telophase steps - spindle fibers made of microtubule proteins

Select all of the following that take place during interphase preceding meiosis.

- production of two identical sister chromatids attached at the centromere - replication of DNA - synthesis of proteins and enzymes needed for cell division

Select all of the following that can result from nondisjunction in humans.

- trisomy - an extra copy of a chromosome - failed development due to missing genetic material

Rank the steps of meiosis II in the correct order in which they occur, beginning with the first step at the top.

1. prophase II 2. metaphase II 3. anaphase II 4. telophase II

How many rounds of cell division occur in meiosis?

2

Mitotic divisions yield _____ daughter cells, and meiotic divisions yield _____ daughter cells.

2; 4

A diploid cell is indicated by what abbreviation?

2n

Match the number of chromosomes in a human diploid cell with the correct description.

46 - total number of chromosomes 22 pairs - autosomes 1 pair - sex chromosomes

What are different version of a gene?

Alleles

The image shows two ways that _____ during meiosis I to generate different combinations of chromatids in resulting gametes.

Chromosomes can orient.

____ splits the cell into two cells after telophase I.

Cytokinesis

Categorize the types of cells as diploid or haploid.

Diploid - somatic cell; zygote Haploid - egg cell; gamete

Anaphase I

During anaphase I of meiosis, homologous chromosomes are separated to opposite poles of the cells

______ is the merging of a sperm and an egg to create a diploid zygote.

Fertilization

Cytokinesis

Four separate haploid daughter cells are formed

What statement describes mitosis?

Homologous chromosomes do not pair during prophase.

During what phase of meiosis I does the spindle arrange the homologous pairs of chromosomes along the equator of the cell?

Metaphase I

Telophase II

Nuclear envelope form, spindles disappear

What is a cell with a complete extra set of chromosomes called?

Polyploid

What results in a random mixture of paternal and maternal genetic material in each daughter cell duringg meiosis?

Random orientation of chromosome pairs during metaphase I.

What are sex cells?

Sex cells are haploid and only contain half the amount of genetic information than diploid cells.

What type of reproduction produces offspring that are genetically different from each other and from the parents?

Sexual reproduction

After this homologous pair undergoes crossing over and meiosis, what resulting chromatids will be segregated into different haploid cells?

Two unchanged chromatids, two chromatids with recombined alleles

Nondisjunction of the ____ chromosome during meiosis can produce offspring that are XXX or XXY.

X

In humans, the sex chromosomes of a female are typically ___ and ___; the sex chromosomes of a male are typically X and ___.

X;X;Y

Match each sex chromosome abnormality with the correct name of the condition.

XXX - triplo-X XO - Turner syndrome XYY - Jacobs syndrome XXY - Klinefelter syndrome

Sister chromatids of each chromosome in a cell are separated to opposite poles during

anaphase II

When ____ reproduction occurs in a one-celled organism, the organism replicated its DNA and splits into two genetically identical cells.

asexual

While ____ reproduction is less costly, _____ reproduction is commonly utilized because it generates genetic diversity.

asexual; sexual

The 22 pairs of human chromosomes that are the same in both males and females are called ____.

autosomes

In eukaryotes, a molecule of genetic material and its associated proteins for, a _________, of which humans have 46 in each cell.

chromosome

Metaphase II

chromosomes are arranged along equator of cell

Prophase II

chromosomes condense; nuclear envelopes break up; spindles form

A ____ cell contains two sets of chromosomes, one set of chromosomes inherited from each parent.

diploid

A _____ cell contains two sets of chromosomes, one set of chromosomes inherited from each parent.

diploid

The special haploid cells required for sexual reproduction are called

gametes

Crossing over, random orientation of chromosomes, and random fertilization are mechanisms involved in meiosis and sexual reproduction that generate ______ diversity.

genetic

A ____ cell contains only one copy of each chromosome.

haploid

The abbreviation n or 1n represents a ____ cell.

haploid

Two chromosomes with the same size, centromere location, and gene sequence are called a _____ pair.

homologous

During meiosis I, what do spindle fibers pull apart?

homologous chromosomes

Two matching chromosomes having the same basic structure and same sequence of genes are called a

homologous pair

Homologous chromosomes are slightly different from each other because they

may carry different alleles for the same genes

A cell in which homologous chromosomes arrange in pairs along the equator of the cell is in what stage of cell division?

meiosis I

What process produces daughter cells for growth and repair, but not for sexual reproduction?

mitosis

A process called ____ occurs throughout the life cycle of an organism, whereas ______ occurs only during gamete production.

mitosis; meiosis

In cell division called _____, the chromosome number in the daughter cells is the same as that in the parent cell, but in cell division called _____, the chromosome number in the daughter cells is half the number present in the parent cell.

mitosis; meiosis

A process called _____ is an error in meiosis in which chromosomes fail to separate and a gamete with too many or too few copies of a particular chromosome can be produced.

nondisjunction

Crossing over only occurs in

prophase I of meiosis

In sexual reproduction, exactly what egg cell matures and what sperm cell fertilizes the egg is

random and results in genetic variability

The ____ are the genetic components that determine whether a mammal develops as a male or female.

sex chromosomes

Anaphase II

sister chromatids are pulled apart and move to opposite poles

In meiosis I, homologous chromosomes separate, whereas in meiosis II,

sister chromatids separate

Other than the germ cells, all diploid cells in the body are called _____ cells, which are able to undergo mitosis but do not undergo meiosis.

somatic

The number of chromosomes in the daughter cells after mitosis is _____ the parent cell, and after meiosis the number is ____ the parent cell.

the same as; half that of

The most common cause of Down syndrome is

trisomy 21

The first diploid cell of a new organism, called a ____, has a set of chromosomes from each parent.

zygote