meiosis and genetic variability

module 3.2

reproduction

in reproduction, genes the genetic information units, are passed to offspring

sexual reproduction

production of genetically different offsprings through fertilization

asexual reproduction

production of genetic identical offsprings (clones) without fertilization

what reproduction is more effective at producing offspring?

sexual reproduction

which way of reproduction give more chance of genetic variation among offsprings?

sexual reproduction

chromosomes

intercellular structures made of proteins and DNA that serves to fold and pack an enormously long DNA double helix

one chromosome includes how many genes?

serval hundred to a few thousand genes

a genes locus

the genes specific location along the length of a chromosome

diploid cell

a cell conatining 2 sets of chromosomes (2n), one set inherited from each parent

haploid cell

a cell containing only 1 set of chromosomes (n)

karyotype

a display of condensed and duplicated chromosome pairs of a cells arranged by size and shape

homologous chromosomes/ homologs/a homologous pair

one from the father and the other from the mother

sex chromosomes

in humans the x and y chromosomes

autosomes

in humans in humans chromosomes 1-22

fertilization

the union of two haploids gametes to produce a zygote, a fertilized egg

the human life cycle

fertilization and meiosis alternate in sexual life cycles, maintaining a consistent number of chromosomes from generation to generation

meiosis

a type of cell division that reduces the number of chromosomes sets from two to one

in meiosis how many duplication of chromosomes followed by two consecutive rounds of cell division?

a single duplication

how many times do chromosomes duplicate in interphase?

once

in meiosis 1 is the

first nuclear division, that separates homologous chromosomes

meiosis2 is the

second nuclear division, that separates sister chromatids

interphase

chromosomes duplication because of chromosomal DNA replication

each duplicated chromosomes consists of how many sister chromatids?

two sister chromatids

each duplicated chromosomes are held together all along by?

they are held all along their lengths via sister chromatid cohesion

gene mutations create different versions of genes called?

alleles

reshuffling of alleles during sexual reproduction leads to?

the most gene

independent assortment of chromosomes happen in?

meiosis1

crossing over happens in?

meiosis1

sources of genetic diversity

random Fertilization

independent assortment of chromosomes

homologous pairs of chromosomes orient randomly in meiosis1

can a gamete receive any combination of maternal and paternal homologues?

yes they can

crossing over

the exchange of matching regions between non-sister chromatid of homologous chromosomes during meiosis

what happens at the beginning of meiosis1?

at the beginning of meiosis1, homologous chromosomes pair up and are precisely aligned gene by gene

each pair must have one or more crossovers because?

it helps hold the homologous pair together as a tetrad

recombinant chromosomes

chromosomes with new combinations of maternal and paternal alleles which are generated by crossing over

chromosomes with the paternal configurations contain?

genes only from the father or from the mother

chromosomes with novel combinations of gene alleles contain?

genes from both parents

random fertilization

a chance event in sexual production which is adds further genetic variation to the offspring

how many different gametes can each human parent produce?

each human parent can produce over 8 million potentiality different gametes

any two human parents will produce a zygote over

7 trillion (>2²³ x 2²³) possible diploid chromosomes combinations