AP bio unit 5

What are gametes? What are they used for?

gametes are sex cells (sperm, egg) gametes are used for reproduction

what are gametes? how are gametes made?

gametes are sex cells made by meiosis

alleles

genes that are slightly different

what does crossing over create?

genetic variation

mitosis purposes (3)

growth, repair, asexual reproduction

*haploid chromosome number is

half the diploid number

What does haploid mean?

haploid means half, this is why sperm and eggs which are haploids need to come together to fertilize a egg. the sperm provides 23 chromosomes whereas the egg provides the other 23 chromosomes; cell now becomes a diploid

Define monosomy.

having only one copy of a particular chromosomes (this is NOT the same as haploid, it is only one chromosome missing)

most genes are

homologous

how are homologous chromosomes different from sister chromatids?

homologous chromosomes are matching chromosomes (one from mom and one from dad) sister chromatids are duplicated chromosomes

metaphase 1 - what moves to the middle of the cell? what is independent assortment?

homologous chromosomes or tetrads (set of 4) move to the middle of the cell independent assortment - how homologous chromosomes or tetrads randomly align along the metaphase plate; this is the second source of genetic variation in sexually reproducing populations

anaphase 1 - what are separated? does it occur in mitosis? explain.

homologous pairs are separated to opposite sides of the cells this does not occur in mitosis because their are no tetrads in mitosis, in meiosis tetrads or pairs are being pulled apart and become sister chromatids and in mitosis sister chromatids are being pulled apart into single strands of chromosomes

In nondisjunction, what happens when homologous chromosomes fail to separate in anaphase I?

if homologous chromosomes fail to separate in anaphase 1 then some daughter cells will have more chromosomes and some will have less

what are homologous chromosomes? where did we get them?

matching chromosomes (a diploid; 2 sets) we got one from our mom and one from our dad, NOT sister chromatids because NOT duplicated

do homologous chromosomes pair up and form a tetrad in mitosis, meiosis, both, or neither?

meiosis

does a synapse occur in mitosis, meiosis, both, or neither?

meiosis

does crossing over occur in mitosis, meiosis, both, or neither?

meiosis

where does meiosis occur and what does it produce?

meiosis occurs in reproductive organs and it produces gametes; sex cells (sperm and egg cells)

does independent assortment occur in mitosis or meiosis?

meiosis only

how did the cells produced at the end of mitosis compare to the cells produced at the end of meiosis 1?

mitosis: diploid, identical to parent cell, identical to each other meiosis: haploids, sister chromatids (need another round of division)

what is the major difference between mitosis metaphase and meiosis metaphase 1?

mitosis: individual chromosomes line up along the center of the cell (sister chromatids) meiosis: homologous chromosomes line up along the center of the cell (tetrads) - second form of variation in meiosis

what is the difference between prophase in mitosis and prophase 1 of meiosis?

mitosis: sister chromatids present meiosis: tetrads present (4 homologous chromosomes), crossing over (1st form of variation) occurs

how is monosomy different from haploid?

monosomy - having one copy of a SPECIFIC chromosome haploid - having half of the diploid amount of chromosomes

how is monosomy different from trisomy?

monosomy - having only one copy of a specific chromosome trisomy - an organism has a third copy of a chromosome that should be present in two copies (present from when crossing over occurs, when that occurs you have three types of chromosomes)

does the number of chromosomes double in mitosis, meiosis, both, or neither?

neither

can humans go through asexual reproduction?

no

does independent assortment occur in metaphase one and two?

no, just metaphase one

what is nondisjunction?

occurs when homologous chromosomes fail to separate in anaphase 1 resulting in some daughter cells with more chromosomes and some with less; error in cell division

mitosis - how many rounds of division?

one

number of cell divisions in mitosis?

one

What happens when sister chromatids fail to separate in anaphase II?

only half of the daughter cells or gametes have an abnormal amount of chromosomes whereas the other half are perfectly fine

what is synapsis?

pairing of homologous chromosomes; formation of a tetrad

what is a chiasma?

point of contact when crossing over (these chromosomes are now NOT homologous because the crossing over makes the chromosomes different from each other; no longer matching)

a women produces 4 gametes through meiosis, however only one becomes a egg. What are the other 3 gametes that eventually dissolve called?

polar bodies

meiosis - what is produced? what is this type of cell division used for?

produced: gametes (sex cells) *primarily used for sexual reproduction

mitosis - what is produced? What is this type of cell division used for?

produced: somatic cells (body cells) *primarily used for growth and repairment

where does mitosis occur and what does it produce?

produces body cells; somatic cells mitosis occurs everywhere in the body besides the reproductive organs

in which stage of meiosis does crossing over occur?

prophase 1

what does malignant mean? (unrelated)

rapidly growing

gametes

sex cells (haploids; 23 chromosomes)

meiosis purpose

sexual reproduction

what separates in mitosis' anaphase?

sister chromatids

anaphase 2 - what is being separated to opposite poles?

sister chromatids are being pulled apart to opposite sides of the cell

what happens to the number of chromosomes in mitosis?

stay the same

prophase 1 - what is a tetrad? What is crossing over? What does it create?

tetrad - occurs when two homologous chromosomes pair up; a tetrad is composed of two homologous chromosomes and four sister chromatids crossing over - when homologous chromosomes are in tetrads during prophase 1, the homologous exchange sections of DNA ; this creates a brand new DNA sequence AND recombinant chromosomes (this is just one important source of genetic variation in sexually reproducing populations)

what separates in meiosis' anaphase 1?

tetrads or pairs, this ensures that gametes are haploid cells

what will happen if a zygote is missing an autosomal chromosome?

that zygote will fail to develop during its time in the womb, a missing chromosome will always result in a miscarriage

diploid chromosome number is

the full diploid number

what can you see in a karyotype?

the number of chromosomes 1-22 + a X (haploid)

telophase/cytokinesis 1 - are these cells haploid or diploid? explain.

these cells are haploid and are now "sister chromatids"

what happens to the number of chromosomes in meiosis?

they are halved

metaphase 2 - how is this different from metaphase 1? how is it similar to mitosis?

this is different from metaphase 1 because now sister chromatids are lining up in the center of the cell, NOT tetrads like in metaphase 1. metaphase 2 is similar to mitosis because in mitosis the chromosomes also line up in the center of the cell before anaphase (where they are split)

meiosis - how many rounds of division?

two

number of cell divisions in meiosis?

two

mitosis - are the cells produced haploid or diploid?

two identical diploid cells

What does diploid mean?

two sets of chromosomes

chromatin

uncondensed DNA

prophase 2 - why does meiosis II need to occur?

we need meiosis II to occur because these chromosomes are now sister chromatids, so the cells need to divide once more to get single strands of chromosomes

if meiosis produces 4 haploid cells they why don't women have 4 eggs per cycle?

women only have one egg per cycle because out of the 4 haploid cells produced one hogs or gets all of the cytoplasm when dividing of these cells occur so the other 3 become polar bodies that will eventually disintegrate and then women are just left with one egg or haploid cell

which chromosome is larger x or y?

x is larger

what does prophase in mitosis have in common with prophase 1 of meiosis?

-both prophase's have six chromosomes -nuclear envelope breaks down -chromosomes condense

number of daughter cells produced in mitosis + are they unique or not?

2 identical daughter cells

number of daughter cells produced in meiosis + are they unique or not?

4 unique daughter cells

sexual reproduction

A reproductive process that involves two parents that combine their genetic material to produce a new organism

autosomes

Chromosomes that are not directly involved in determining the sex of an individual.

which meiosis is similar to mitosis

Meiosis II

explain how Mendel's law of independent assortment relates to metaphase 1 and how it creates variation in offspring

Mendel's law of independent assortment relates to metaphase 1 because in metaphase 1 chromosomes line up in random order in the center of the cell before they are split in anaphase and Mendel's law of independent assortment is effected by where these chromosomes line up. This creates variation in offspring because the order in which chromosomes line up in metaphase 1 determines which chromosomes and genes go to which daughter cell.

asexual reproduction

Process by which a single parent reproduces by itself

women have how many x and how many y chromosomes?

XX

men have how many x and how many y chromosomes?

XY

what is a recombinant chromosome?

a brand new DNA sequence (is present after crossing over occurs)

recombinant chromosomes

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

what occurs after two haploids have come together?

a diploid is formed (two sets of chromosomes) and now the cell can divide through mitosis to become a full organism

What is formed during fertilization?

a diploid; zygote

in a haploid, what type of chromosome is the 23rd chromosome?

a sex chromosome

What does aneuploid mean?

abnormal number of chromosomes.

telophase/cytokinesis 2 - how would you describe these cells? what are two sources of variation?

after telophase/cytokinesis 2 you end up with four genetically different haploid cells 1st source of variation - crossing over that result in recombinant chromosomes 2nd source of variation - the way at which the homologous chromosomes line up during metaphase 1

independent assortment

alleles of a gene separate once gametes form

how does anaphase determine if a daughter cell is going to be haploid or diploid?

anaphase 1 splits the tetrads ensuring that the daughter cell is haploid because you are splitting the chromosome number in half

*if both chromosomes are split in anaphase for mitosis and meiosis then why does one create a haploid and one a diploid?

because a sister chromatid is one chromosome. even though sister chromatids are split in the anaphase in mitosis, they go from one chromosome to one chromosome, whereas in meiosis these are tetrads, so they go from two chromosomes to one chromosome

why is a second round of division necessary for the production of haploid gametes?

because at the end of meiosis I the chromosomes are sister chromatids since they started at tetrads, so they need another round to split once more

How did lining the homologous chromosomes up in pairs help to ensure haploid cells would be produced?

because these pairs or tetrads are two chromosomes, so if we wanted to split this number in half we can, whereas sister chromatids are one chromosome, so we can't split these in half

the cell that starts meiosis is a diploid cell. Describe the DNA content of the cell before meiosis begins.

before meiosis begins there are two of each kind of chromosome

somatic cells

body cells (diploids; 46 chromosomes)

How do our body cells compare to gametes? (Which process makes them, how many chromosomes do they have?)

body cells: 46 chromosomes, produced by mitosis gamete cells: 23 chromosomes, produced by meiosis

do mitosis, meiosis, or both occur after interphase?

both

meiosis

cells division that produces gametes (sex cells that are haploids)

what occurs in prophase 2?

chromosomes condense, spindles fibers form in each new cell, fibers attach to chromosomes, nuclear envelope breaks down (similar to prophase in mitosis)

are chromosomes condensed or uncondensed when DNA is dividing?

condensed

chromosomes

condensed DNA

explain how crossing over and independent assortment contribute to the variation seen in the four gametes produced at the end of meiosis II

crossing over mixes up the genes within their tetrad, and independent assortment has to do with the random lining up of tetrads or pairs in the center of the cell before they are split, this causes variation in the four gametes produced at the end of meiosis II because it mixes around chromosomes and genes

does crossing over occur in mitosis? why or why not?

crossing over never occurs in mitosis because chromosomes that undergo mitosis don't form tetrads, and you can't have crossing over take place if you don't first have a tetrad

meiosis - describe the genetic composition of the cells

daughter cells are genetically different to parent cell

mitosis - describe the genetic composition of the cells

daughter cells are genetically identical to parent cell

alleles

different versions of a gene

haploid + haploid =

diploid

T or F, both mitosis and meiosis start with duplicated chromosomes

false, mitosis chromosomes are duplicated whereas the chromosomes in meiosis are homologous chromosomes (matching)

synapse (cell division)

formation of a tetrad

meiosis - are the cells produced haploid or diploid?

four unique haploid cells

What kind of cells are made by meiosis? Are they haploid or diploid?

gamete cells are made by meiosis they are haploid cells (one set of chromosomes)