Chapter 10

There are 23 pairs of chromosomes and 2 sets.

# of pairs of chromosomes # of sets of chromosomes

Crossing over produces

chromosomes with new combinations of materal and paternal alleles.

The chromosome number of a species generally correlates with the size or complexity of its genome. True or False

False

Genetic differences occassionally arise in asexually reproducing organisms as a result of:

changes in DNA called mutations

The X and Y chromosomes are called ___ , the other chromosomes are called ___.

sex; autosomes

Any cell with two chromsome sets

diploid

Which letter represents the sister chromatid

F

identify the homologous pair

G

Gametes contain ____ set of chromosomes

a single set

Which letter represents the gene loci

H

Meiosis ___ is like mitosis.

I

A hydra reproduces asexually by

budding

1. 2 sets of chromosomes are present. 2. three pairs of homologous chromosomes are present

1. # of chromosomes present 2. # of pairs of homologous chromosomes

The set of chromosomes of a gamete consists of ___ autosome(s) and ___ sex chromosome(s).

22 autosomes, 1 sex chromsome

If the DNA content of a diploid cell in the G1 phase of the cell cycle is x, then the DNA content of the same cell at metaphase of meiosis I would be

2X

Humans have ___ chromosomes in their somatic cells.

46

The fusion of a male gamete with a female gamete during fertilization will produce a zygote with an y of about ____ diploid combinations

70 trillion

Each gamete that you produce in your lifetime contains one of roughly ____ possible combinations of chromosomes.

8.4 million

Which letter represents the kinetochore

A (pointing to the black part)

Is a set of chromosomes haploid or diploid?

A set of chromosomes is always haploid.

Identify the stage of Meiosis shown

Anaphase II

In prophase I, homologous chromosomes pair up and undergo crossing over. Can this occur also during prophase II? Explain.

At the end of meiosis I, the two members of a homolgous pair end up in different cells, so they cannot pair up and undergo crossing over during prophase II.

The genetic program of our genes is written in the language of __.

DNA, the polymer of four different nucleotides.

Identify the gene chiasma

E

identify the sister chromatid cohesion

F

Only animals, not plants reproduce sexually, alternating meiosis with fertilization. True or False.

False, both plants and animals

___ is the raw material for evolution by natural selections.

Genetic variation

Each of the six chromosomes is duplicated, so each contains two DNA molecules, so thre are 12 DNA molecules in this cell.

How many DNA molecules (double helices) are present?

Which letter represents nonsister chromatids.

I

A certain eukaryote lives as a unicellular organism, but during environmental stress, it produces gametes. The gametes fuse, and the resulting zygote undergoes meiosis, generating new single cells. What type of organism could this be?

It must be a fungi or a protist

The two homologs of a pair move toward opposite poles of dividing cell during

Meiosis I

Identify the stage of meiosis shown

Metaphase I

____ makes it possible for organisms to reproduce asexually.

Mitosis

Each sperm of a pea plant contains seven chromosomes. What are the haploid and diploid numbers of this species.

The haploid (n) is 7; the diploid number (2n) is 14

If materal and paternal chromatids have identical alleles, will crossing over lead to genetic variation?

The recombinant chromosomes will be genetically equivalent to parental chromosomes

How do you know this cell is undergoing meiosis

The two homologs of a homologous pair are associated with each other at the metaphase plate. Chiasmata are clearly present (crossover has occurred). These processes do not occur in mitosis

Crossing over contributes to genetic variation only when it involves the rearrangment of different alleles. True or False.

True

Crossing over produces some parental gametes with chromosomes like that of the parents and some recombinant gametes with a mixture of genes from both sets of chromosomes. True or False

True

Either halooid or diploid cells can divide by mitosis, depending on the type of life cycle. True or False

True

Only diploid cells can udergo meiosis, while haploid cells can undergo mitosis or meiosis. True or False

True

Sexual reproduction produces greater genetic variation than asexual reproduction. True or false.

True

n=3

What is the haploid number (n) of this cell?

If the DNA content of a diploid cell in the G1 phase of the cell cycle is represented by x, then the DNA content of the same cell at metaphase of meiosis I would be 2x. If we continue to follow the cell lineage, the DNA content of a cell at metaphase of meiosis II would be:

X

An unfertilized egg contains a(n)__ chromosome; a sperm contains a(n) __ chromosome.

X; X or Y

karyotype

a display of the chromosome pairs of a cell arranged by size and shape.

The human life cycle begins when ___________ in a process called fertilization.

a haploid sperm from teh father fuses with a haploid egg from the mother.

The life cycle is comlete as the zygote develops into

a sexually mature diploid adult.

A life cycle in which there is both a multicellular diploid form, the sporophyte, and a multicellular haploid form, the gametophyte; characteristic of plants and some algae.

alternation of generations

Type of life cycle of plants and some algae

alternation of generations.

All sexual life cycles involve

an alternation of diploid and haploid stages

An individual that reproduces asexually gives rise to a __.

clone

Homologs appear alike in the microscope, but they may have ....

different versions of genes at the corresponding loci.

each sexually reproducing species has a characteristic

diploid and haploid number

In most fungi and some protists, gametes fuse and form a ___ zygote. ___ occurs without a multicellular diploid offspring developing.

diploid zygote; Meiosis

Homlogs are not associated with each other in any obvious way except

during meiosis

Meiosis results in ___ daughter cells.

four

In animals and plants, reproductive cells called ___ are the vehicles that transmit genes from one generation to the next.

gametes

cells of the gametophyte give rise to... by...

gametes; mitosis

Gametes develop from specialized cells called

germ cells

In each generation, the number of chromosome sets is ______ during meiosis, but _____ at fertilization.

halved; doubled

In fungi and protists, meiosis produces ____ that divide by ____.

haploid cells; mitosis.

Meiosis produce____ and fertilization produces ___.

haploid gametes; diploid organisms.

Typically, human females have a ___ pair of X chromosomes.

homologous

If a gene for eye color is situated at a particular locus on a certain chromosome, its ____ will have a verson of the eye-color gene at the equivalent locus.

homologous chromosome

The chromsome number of a species reflects:

how many linear pieces of DNA make up the genome.

Three mechanisms that contribute to the genetic variation arising from sexual reproduction

independent assortment of chromosomes; corssing over; random fertilization

Two chromosomes of a homologous pair are ____.

individual pairs.

In meiosis, after the chromosomes duplicate in ____, the diploid cell divides -----

interphase; twice, yielding 4 daughter cells.

Even though the chromosomes are duplicated, we still say the cell is diploid, or 2n. This is because

it has only two sets of information regardless of chromatids.

___ can be used to screen for defective chromosomes or abnormal numbers of chromosmes associated with certain congentical disorders, such as down syndrome

karyotyping

A gene's specific location along the length of the chromosome

locus

Genetic expression in sexually reproducing organisms is dictated by the production of ____, the genes program cells to make specific enymes and other proteins, whose cumulative actions produces an individuals's inherited traits.

mRNAs

____ in the sporophyte produces haploid cells called spores.

meiosis

Phase of mitosis where chromosomes are most condensed.

metaphase

Identify the phase of meiosis

metaphase II

During karyotyping cells arrested when chromosomes are in ____ phase of mitosis.

metaphase.

An asexually reproducing eukaryotic reproduces by _____, which generates offspring whose genomes are exact copies of the parent's genome in the absence of mutation.

mitosis

After fertilization, the diploid zygote divides by:

mitosis.

The original source of different alleles

mutations

Together, the sister chromatids make up

one duplicated chromosome

Is meiosis in humans, an average of ____ crossover events occurs pur chromosome pair.

one to three

A special kind of cell division called meiosis occurs in the ____ and ___ producing ____ gametes, a sperm and an egg.

ovaries and testes; haploid

Identify the phase of meiosis

prophase II

Chromosome created when crossing over combines DNA from two parents into a single chromosome.

recombinant chromosome

Independent assortment and crossing over occur:

simultaneously duirng meisosis

A human cell containing 22 autosomes and a Y chromosome is

sperm

Identify the phase of Meiosis

telophase I

Identify the phase of meiosis

telophase II

If human gamets were made by mitosis, during fertilization:

the normal chromosome number would double to 92

A yeast cell or an amoeba is the sole parent of its offspring. True or false

true

Each metaphase chromosome consists of

two closely attached sister chromatids

Sister chromatids are

two copies of one chromosome

In a cell in which DNA synthesis has occured, all the chromosomes are duplicated, therefore each consists of

two identifcal sister chromatids.