human genetics

what are somatic cells?

non reproductive cells (most cells)

dont produce gametes, diploid, cell division 2 copies of each chromosome

describe human chromosomes (number, pairs, autosomes)

46 human chromosomes - 23 homologous pairs

22 are autosomes(nonsex) 1 thourgh 22

23rd pair is s ex chromosomes

what is the point of the cell cycle

series of events, cell growth, dna replication and cell division

result in 2 daughter cells - genetically identical to parent cell

interphase and mitotic phase

what happens in interphase?

normal process, preparing for cell division tho

three stages

G1 - first gap, no visible change but cell accumulates building blocks DNA and energy

S - DNA replication - 2 copies of chromosomes(sister chromatids), centrosome duplicates - mitotic spindle - movement of chromosomes

G2 - second gap, cell replenish energy, organelles duplicated, mitotic spindle dismantled, grows in size to prepare for mitotic phase

what is the secret g0 stage?

some cells will exit cell cycle and enter g0, inactive stage, can br triggered by cellular cues to reenter cycle

whats the difference between sister chromatids and homologous chromosomes

sister chromatids are joined to its copy by centromere(kinetochore)- identical replicated copies

homologus chromosomes - pair of seperate chromosomes, one from each parent

describe the mitotic phase

make two daughter cells

prophase - condensing of chromosomes, spindle fibers merge, movement

metaphase - lined up at metaphase plate, sister chromatids attach to spindle fiber

anaphase - centromeres split, pulled towards opposite poles

telophase - at opposite poles, begin decondense, mitotic spindle breaks down

cytokinesis - filaments constrict, form cleavage seperates daughter cells

what is meiosis (meiosis I)

human germ cells form gametes - produce 4 daughte cells (1n) haploid/half # of chromies

in meiosis 1: 2 haploid daughter cells

prophase 1 = condense, CROSSING OVER(homologous pairs exchange genetic material)

metaphase 1 - move to equator

anaphase 1 - move to opposite poles SEPERATION OF HOMOLOGOUS CHROMOSOMES

telophase 1 - gather at poles, divide

what happens and outcome of meiosis II

prophase II - sindle forms around chromosomes

metaphase II - line up at equator

anaphase II - centromeres divide, move to opposite poles of cell SEPERATION OF SISTER CHROMATIDS

telophase/cytokinesis - envelope forms, cytoplasm divides

result in 4 daughter cells total,

define genotype, gene, phenotype, allele

genotype - genetic makeup

gene - code for amino acifd sequence - make protein

phenotype - characteristic code

allele - code for variation of characteristic - trait

homozygous vs heterozygous

humans are diploid 2 alleles for each gene

homozygous - two identical alleles

heterozygous - two different alleles (one may be dominant)

human traits can be much more complex (50 genes for eye colour) - 2 alleles each

who was mendel, what were his hybridization experiments

scientist, uses pea plants as primary model system to study inheritance patterns

30,000 pea plants, demonstrates that traits are transmitted from parents to offspring in specific patterns

hybridizations - mating two individuals with two different traits for a single characteristic

• in pea plants, would be colour of flower petals - character trait would be white colour

what is the law of segregation

paired genes must seperate equallty into gametes, so offspring have an equal likelihood of inherting each gene -

ANAPHASE of meiosis I - homologoud pairs seperate

whats the difference between autosomal dominant and recessive

autosomal dominant - dominant allele on autosome

autosomal recessive - allelle causes a disorder on an autosome

what is X linked, x linked dominant and recessive

x linkage - when gene examined is present only on X chromosome

dominant - when its on the x chromosomes - more females affected

recessive - more males affected can only have it or not, females can be homozygous or heterozygous

what are lethal alleles?

alleles that result in failure of development in utero/shortening of lifespan

2 receeive lethal alleles - death, 1 dominant - death

• huntingtons disease - nerve cell degeneration but not noticable till reproductive age

how do mutations arise

DNA copying errors, environmental causes like radiation or toxic chemcals

impact sequence of amino acids that make a protein

what are some chrosomal disorders

occur during metaphase I or II of meiosis, fail to seperate, move to opposite poles, nondisjunction!

downsyndrome - extra copy of chromie #21

turnder syndrome - 1 X chromosome

kleinfelter - 2 X 1 Y

can do a DNA test - small dvolume of blood to determine if person carries defect allele