AP Bio - ch. 13

Role in the animal body: Mitosis

- enables multicellular adult to arise from zygote - produce cells for growth, repair, and in some species, asexual reproduction

What is the purpose of meiosis?

- genetic variance - replicates chromosomes and divide cells

Explain what occurs in each, and how this increases diversity: independent assortment of chromosomes

- homologous pairs of chromosomes position randomly - metaphase I - 2n

Where are the gametes of an animal produced? Be specific as to male and female gametes.

- male gametes are called sperm - female gametes are called eggs

Number of DNA replications: Mitosis

- occurs during interphase before mitosis begins

Chromosome number of daughter cells: Meiosis

- occurs during prophase I along with crossing over between nonsister chromatids - resulting chiasmata hold pairs together due to sister chromatid cohesion

Sex chromosome: explanation and number in human cells

- one pair that contains genes that determine your gender - 2 total=2 X in females and 1 X and 1 Y in males

How is the arrangement of chromosomes different from metaphase of mitosis?

- pairs of homologous chromosomes are moved by the spindle fibers to the equator - chromosomes made of the two chromatids remain together

Role in the animal body: Meiosis

- produces gametes - reduces number of chromosomes by half and introduces genetic variability among gamates

autosome: explanation and number in human cells

- the 22 pairs of chromosomes that are NOT involved in determining your gender - 44

Explain what occurs in each, and how this increases diversity: crossing over

- the exchange of genetic material between nonsister chromatids during synapsis of meiosis I

What are alleles? Give an example.

- versions of genes - ex. blood type: A,B,O

*****chromosome number is reduced in meiosis I and that the daughter cells at the end of meiosis I are haploid*****

...

How many times do the chromosomes duplicate?

1

How many times does the cell divide in meiosis?

2

Number of divisions: Meiosis

2, each including prophase, metaphase, anaphase, and telophase

Therefore, since humans have 46 chromosomes or 23 homologous pairs, what is the number of possible gametes that can be formed due to independent assortment of chromosomes?

2^23 or 8.4 million

How many daughter cells are formed?

4

The muscle cells of a dog have 78 chromosomes. Fill in the correct chromosome number in a: bone cell_______ sperm_______ haploid cell_______ somatic cell_______ zygote_______

78;39;39;78;78

prophase I

chromosomes condense and nucleur envelope breaks down

What occurs in synapsis?

chromosomes move together

haploid or diploid: liver cell

diploid

haploid or diploid: skin cell

diploid

haploid or diploid: somatic cell

diploid

haploid or diploid: zygote

diploid

Chromosome number of daughter cells: Mitosis

does not occur

Synapsis and crossing over are unique to meiosis. During what specific phase do these occur?

during prophase I, replicated homologous pair up and become physically connected along their lengths by a zipper-like protein structure, the synaptic complex

Are the resultant daughter cells haploid, or diploid?

haploid

haploid or diploid: egg

haploid

haploid or diploid: gamete

haploid

haploid or diploid: sex cell

haploid

haploid or diploid: sperm

haploid

What is the chromosome number?

haploid #

female gamete

haploid cells

male gamete

haploid cells

gamete

haploid sex cells that are used for reproduction

There will be two divisions in meiosis. What will separate in the first division in meiosis I?

homologous chromsome pairs separate not chromatids

locus

location of gene on chromosome

By what process are gametes produced?

meiosis=the process which turns diploid cells into haploid cells

Study the events of prophase I as they are significant. Explain each of these events: synapsis

moving together

Number of DNA replications: Meiosis

occurs during interphase before meiosis I begins

asexual reproduction

one parent cell, cloning

Number of divisions: Mitosis

one, including prophase, metaphase, anaphase, and telophase

What is crossing over?

parts are changed within chromatids

Study the events of prophase I as they are significant. Explain each of these events: crossing over

parts of a chromatid are broken and exchanged with corresponding portions on the other homologous chromosome

What happens to chromosome number in meiosis?

reduced

What is the purpose of meiosis?

replication of chromosomes and cell division

gene

segments of DNA that code for a protein or RNA molecule

During meiosis I, homologous chromosomes separate. What separates during meiosis II?

sister chromatids separate

How does a somatic cell compare to a gamete in terms of chromosome number?

somatic: - diploid (2n) - containing 2 sets of chromosomes - 23 pairs, 46 chromosomes gamete: - haploid (n) - single set of chromosomes - 23 chromosomes in humans

genetics

study of heredity and hereditary variation

chiasma (plural, chiasmata)

the physical manifestation of crossing over, it appears as a cross because sister chromatid cohesion still holds the 2 original sister chromatids together, even in regions where one of them is now part of the other homolog.

What are homologs (homologous chromosomes)?

the same gene that could have different alleles

heredity

transformation of traits

sexual reproduction

two parent cells, variation

Study the events of prophase I as they are significant. Explain each of these events: chiasmata

where it happens

Explain what occurs in each, and how this increases diversity: random fertilization

- 1 sperm (1 of 8 million possible chromosome combinations) - 1 ovum (same)= 64 trillion chromosomes

Number of daughter cells: Mitosis

- 2, each diploid (2n) - genetically identical to the parent cell

Number of daughter cells: Meiosis

- 4, each haploid (n), containing half as many chromosomes as parent cell - genetically different from parent cell and from each other

How many chromosomes are in human cells? What is a chromosome?

- 46 - a cellular structure carrying genetic material, found in the nucleus of eukaryotic cells

What is a karyotype? How is it prepared? What are three things that can be determined from a karyotype?

- a photo of the chromosomes in a dividing cell - extra chromosomes - boy/girl

What is a somatic cell? Give examples of two human somatic cell types.

- any cell other than those involved in gamete formation - has 46 chromosomes - 23 from mom and 23 from dad - non-gametes

homologous chromosomes

- chromosomes in a pair - same shape, size and genes

Explain what is meant by homologous chromosomes.

- chromosomes in a pair, same shape, size and genes (different alleles)

Explain the physical events of crossing over. You may wish to make a sketch of the event. Include these terms: synaptonemal complex, chiasmata, homologs, sister chromatids.

- during prophase I, replicated homologous pair up and become physically connected along their lengths by a zipper-like protein structure, the synaptic complex - then, genetic rearrangement between nonsister chromatids, known as crossing over, is completed - two homologous pull apart slightly but remain connected by at least one x-shaped region called the chiasma, synapsis and crossing over normally don't occur during mitosis

Which type of reproduction will result in genetically identical offspring?

asexual reproduction

sexual: advantage and disadvantage

advantage=genetic diversity disadvantage=must have mate

asexual: advantage and disadvantage

advantage=many offspring in short amount of time disadvantage=no genetic diversity

During which division is the chromosome number reduced?

anaphase

What is another term for a fertilized egg? __________________What is the chromosome number of the fertilized egg? (Answer this in general terms, haploid, n, or diploid, 2n.)

zygote;diploid