intro to genetics

stage one of meiosis I

prophase I

stage two of meiosis I

metaphase I

stage three of meiosis

anaphase I

stage four of meiosis I

telephase I

stage five of meiosis I

cytokinesis I

prophase I

homologus pair, crossing over, chromosomes condenses, spindles form. nuclear envelope fragments

metaphase I

shortest phase, homologus pairs of chromosomes line up across the center of the cell

anaphase I

homologus chromosomes separate and move to opposite poles, sister chromatid are still attached at their centromeres

telephase I

nuclear envelope reassembly, spindle disappears

cytokinesis I

divides the cytoplasm into two parts by cleavage furrow

stage one of meiosis II

prophase II

stage two of meiosis II

metaphase II

stage three of meiosis II

anaphase II

stage four of meiosis II

telephase II

stage five of meiosis II

cytokinesis II

prophase II

similar to prophase of mitosis, nuclear envelope fragments, spindle forms, chromosomes are still double

metaphase II

chromosomes (two sister chromatids) line up across the center of cell

anaphase II

centromere split & sister chromatids separate and move to opposite poles

telephase II

nuclear envelope reassembles, chromosome decondenses, spindles disappear

cytokinesis II

divide cell into two by cleaevage furrow

what is a gamete

sex cells

how many chromosomes does gametes have

23

what us a homologus chromosome

contains the same genes, but they may be in different forms. sister chromatids are identical copies of a chromosome

when is sexual reproduction more advantageous than asexual reproduction

when the environment is changing or is unlivable

what is crossing over

the two pairs of homologus joint together very close. two non-sister chromatids are crossed over at a chiasma point and exchange corresponding segment. new combo of traits

what stage of meiosis does crossing over occur?

prophase I

what is fertilization

the sperm fuses with the egg and the egg becomes fertilized

homozygous vs. heterozygous

homozygous has two identical alleles and heterozygous has two different alleles

dominant vs. recessive traits

dominant is stronger of two genes expressed in the hybrid and recessive is a gene that shows up less often in a cross; represented by a lowercase letter

phenotype

physical feature resulting from a genotype

genotype

gene combination for a trait

how do you know what the phenotype will be

based on the genotype

law of segregation

during the formation of gamete, the two alleles responsible for a trait separate from each other. alleles for a trait are “recombined” at fertilization, producing the genotype for the traits of the offspring

law of independent assortment

alleles for different traits are distributed to sex cells (and offspring) independently of one another. they can be illustrated using dihybrid crosses

number of chromosomes in body cells

46

number of chromosomes in egg cells

23