Meiosis

Meiosis produces

cells with half the chromosomes of the parent cell

Humans have ___ chromosomes

96

Meiosis l

homologs are seperated

Meiosis ll

sister chromatids are seperated

A chromosome in a matching pair is a

homolog

Fertilization unites a

sperm and egg re-establishing [air og homologous chromosome with both pateral and materal genes

Offspring resemble

their parents more than they do unrelated individuals

Heredity is the

transmission of traits from one generation to the next

Variation is demonstrated by

the differences in appearance that offspring show from parents and siblings

genetics is the

scientific study of heredity and variation

genes are the

units of heredity and are made up of segments of DNA

A genes specific position along a chromosomes is called its

locus

genes are passed to the next generation via reproductive cells called ____, Human gametes have ____ chromosomes

gametes, 23

Humans have 46 chromosomes in the nuclei of their

somatic cells

In sexual reproduction a single

individual passes all its genes to its offspring without the fusion of gametes

A ____ is a group of genetically idential individuals from the same parent

clone

In ____two parents give rise to offspring that have unique conbinations of genes inherited from the two parents

sexual reproduction

A ___ is the generation-to-generation sequence of stages in reproductive history of a organism

life cycle

Human somatic cells have ___ pairs of chromosomes

23

The two chromosomes in each pair are called

homologous chromosomes or homologs

The fusion of 2 gametes produces

A zygote with any of 79,368,749,177,694 diploid combinations

Mitosis conserves the

number of chromosome sets producing cells that are genetically identical to the parent cell

Meiosis reduces two

number of chromosomes sets from 2(diploid) to one (haploid), producing cells that differ geneticall from each other and from the parent cell

Each pair of homologous chromosomes includes

chromosomes from each parent

A _____ has two sets of chromosome

diploid cell

For humans the diploid # is

46(2n = 46)

A gamete (sperm or egg) contains a single set of chromosomes aND is thus a

haploid cell

For humans the haploid # is

23(n=23)

Behavior of chromosome sets in

the human life cycle

Haploid ( )

n

Diploid ( )

2n

The alteratino of meiosis and fertilization is common to all organisms that

reproduce sexually

the three main types of sexual life cycles differ in

the timing of meisosis and fertilization

like mitosis, meiosis is

prepared by the replication of chromosomes

Meiosis takes place in two consecutive cell division called

meiosis l and meiosis ll

the 2 cell divisions result in

four daughter cells rather than the 2 daughter cells in mitosis

Each daughter cell has only

half as many chromosomes as the parent cell

meiosis l four phases

Prophase l, metaphase l, anaphase l, telohase l and cytokinesis

meiosis ll four phases

Prophase ll, metaphase ll, anaphase ll, telohase ll and cytokinesis

Meiosis l

seperates homologous chromosomes

Meiosis ll

seperates sister chromatids

At the end of meiosis there are

four dauther cells, each with a haplid set of unreplicated chromosomes

Each daughter cell is

genetically distinct from the others and from the parent cell

synapsis and crossing over in prophase l

homologous chromosomes physically connect and exchange genetic info

homologous pairs at the

metaphase plate

seperation of homologs during

anaphase l

Mutations (changes in an organisms DNA) are the

original source of genetic variation

mutations create different

versions of genes called alleles

reshuffling of alleles during reproduction produces

genetic variation

three mechanisms that contribute to genetic variation

mutatinos, crossing over, independent assortment

homologous pairs of chromosomes orient

randomly at metaphase l of meiosis

random fertilization adds

to genetic variation b/c any sperm can fuse with any egg