CH 11

production of offspring through the union of male and female gametes

sexual reproduction

What’s produced during fertilization

zygote

Fertilization

nuclei of an egg an sperm cell fuse producing a zygote

how many chromosomes do gametes have

half from mother half from father

asexual reproduction generates genetically identical offspriing (T/F)

True

Asexual reproduction reproduces through mitosis or meiosis?

mitosis

sexual reproduction produces offspring that are genetically identical (T/F)

False - none of the offsprings are likely to be genetically identical because meiosis and fertilization mix genetic info

sexual reproduction generates _______ that’s the basis of most inherited differences

variability

Where meiosis takes place in humans

gonads

testes

mature gonads of male

ovaries

mature gonads of female

meiosis in testes produce

spermatozoa / sperm

meiosis in ovaries produce

ova /eggs

spermatozoa/sperm

gametes of male

ova/eggs

gametes of female

cellular mechanism of gamete formation

gametogenesis

spermatogenesis

production of sperm

oogenesis

production of eggs

example of gametes

sex cells like sperm or egg cell

example of somatic cell

heart cells, lung cells, skin cells

gametes contain a diploid genome (T/F)

False - contain haploid genome since half comes from mom half comes from dad for diversity

Gametes are involved in asexual reproduction (T/F)

False - only in sexual reproduction

Gametes are restricted to reproductive organs (T/F)

True

Gametes originated from stem cells (T/F)

False - they originate from germ cells

Gametes are not involved in the formation of structures like organs (T/F)

True

In gametes, mutations are not carried of to offspring (T//F)

False = mutations are carried to offfspring

how many chromosomes does human egg or sperm cell have

23 chromosomes

how many chromosomes does zygote haave

46 chromosomes

2 processes that maintain diploid number in body cells as zygote develop

DNA replication

mitotic cell division

when does chromosome return to diploid number of 46 or 23 pairs?

when egg and sperm combine in sexual reproduction to produce zygot

What’s separated in meiosis I

homologous chromosome pairs into 2 daughter cells

What’s separated in meiosis 2?

sister chromatids of each chromosomes separate to 2 daughter cells

how many haploid cells result from meiosi 2

4

When does DNA replicate and chromosomal protein proteins produced in meiosis

premiotic interphase

meiosis is not a reduction division (T/F)

False it’s a reduction division

homologous chromosomes pair and nonsister chromatids undergo physical exchange of chromosome segments

crossing over during meisis 1

completion of meiosis 1 produces how many cells

2 cells

how many chromosomes does each daughter cell have after meiosis 1

23 since they’re haploid. Only time cells are diploid is with parent cell in the beginning

when do sister chromatids separate

meiosis 2

chromatids of homologous chromosomes physically exchange segments

crossing over

parts of prophase 1

1-Leptotene

2-zygotene

3-pachytene

4-diplotene

5-diakenesis

when does synaptoman complex form

zygotene

stage in prophase 1 when crossing over happens

pachytene

stage in prophase 1 when synaptomal complex start to disappear and chiasma becomes visible

diplotene

2 chromosomes of each homologous pair undergo pairing

synapsis

during synapsis these are formed

tetrads

sites where crossing-over has occurred are marked by thickened spots

chiasmata

function of synaptomal complex

hold chromosomes on top of each other during zygotene

synaptonemal complex is meiosis -specific multiprotein complex (T/F)

True

What happens in anaphase 1

• homologous pairs separate

• then move to opposite spindle poles as spindle microtubules contract

each chromosome in anaphase 1 after now only has 1 sister chromatid (T/F)

False still has 2 chromatids

there’s no change in number of chromosomes in telophase 1 (T/F)

true

interkinesis

single spindle of first meiotic division disassembles

microtubules reassemble into 2 new spindles for the second divsion

spindles separate 2 chromatids of each chromosome and pull them to opposite spindle poles

anaphase 2

chromosome segregation happens in

anaphase 2

in telophase 2 chromosome decondense to the

extended interphase state

nondisjunction

spindle fails to separate homologous chromosomes in meiosis 1 or sister chromatids in meiosis 2

in nondisjuntion, 1 pole receives both chromosomes while other pole has no copies of that chromsome (T/F)

true

pairs of chromosomes that are different in male and female individuals of the same species

sex chromosomes

sex chromosomes of females

XX

sex chromosomes of male

XY

Development into male depends ont presence of female chromosome T/F

False depends on presence of gene on Y chromosome

in males XY chromosomes are homologous in the long region T/F

false - homologous in short region

Main advantage of sexual reproduction

Genetic variability

3 sources that increases likelihood of genetic variability

-Crossing over

-independent assortment

-particular sets of male and female gametes that unite in fertilization

Parental chromosomes

2 nuclei receive unchanged chromosomes

Recombinant chromosomes

2 receive chromosomes with new combinations of alleles

Mechanism for genetic recombination

Crossing bc produces genetic recombinants

Only 1 crossing over events may occur in same chromosome pair (T/F)

False - one or more crossing over events may Occur in same chromosome pair involving same or different chromatids

Second major source of genetic variability

Independent assortment

How many combinations does the 23 chromosome pairs allow

2²³ combinations of maternal and patermal combinations

3th factor that increases genetic variability

Chance union of gametes increases gatiability of sexual reproductiom

3 major patterns in life cycles of eukaryotes

• life cycle spent in haploid and diploid phases

• Whether mitotic intervene between meiosis

• Formation of gametes

Meiosis in animals

• diploid phase dominates life cycle / haploid phase reduced

• In males - 4 nuclei = 4 sperm

• Females - 4 nuclei = only 1 egg survive

• Fertilization restores diploid

Meiosis in Plants

• alternate between haploid and diploid generation may dominate life cycle depending on organisms

Fertilization produces the diploid generation

Sporophytes

Some cells of mature sporophytes undergo meiosis produce ———

Haploid spores

Haploid Spores germinate and grow by mitotic division into a generation of

Haploid gametophyte

Spores undergo meiosis to become gametophytes (T/F)

False - go through mitosis

What do gametophyte produce?

Haploid egg and sperm nuclei

term for fungi gametes

plus and minus