Unit 4: Structural Genetics

mitosis

cell division for a eukaryotic, somatic cell to create 2 identical daughter cells

phases of mitosis

interphase (g1, s, g2), mitotic phase (p, m, a, t), cytokinesis

chromatin

unorganized dna

chromatid

strand of chromosomal material

chromosome

two strands of chromosomal material joined together by a centromere

g1

cell growth, protein synthesis, metabolic activities

s

dna replication

g2

cell growth, prepare for mitosis

prophase

longest phase

nucleolus and nuclear membrane disappear

chromatin condenses into chromosomes

spindle fibers form and centrioles move apart

metaphase

shortest phase

chromosomes move to equatorial plate

anaphase

sister chromatids separate and move apart

spindle fibers shorten

telophase

cleavage furrow or cell plate develops

nucleolus and nuclear membrane reappear

chromosomes uncoil

cytokinesis

division of the cytoplasm

2 daughter cells are produced

binary fission

parent cell divides into 2 identical daughter cells

budding

split into 2 or more individuals with offspring identical to parent

fragmentation

organism is made from a piece of the parent organism

spore formation

parent produces hundreds of tiny spores that grow into identical organisms

cyclin dependent kinase (cdk)

enzyme that creates checkpoints for the cell

g1 checkpoint

is cell big enough

is environment good

g2 checkpoint

is dna replicated

is environment favorable

is cell big enough

metaphase checkpoint

are chromosomes lined in the middle

apoptosis

programmed cell death

cancer

uncontrolled division of the cells

tumor

mass of cells

metastasis

cancer moves from original location and grows in a new area of the body

meiosis

cell division of the sex cells to produce gametes where half the number of chromosomes are produced

meiosis 1

homologous chromosomes separate

cell division where number of chromosomes are reduced by half

prophase 1

longest phase (90% of time)

nucleolus and nuclear membrane disappear

spindle fiber forms

chromosomes condense

synapsis, homologous chromosomes form tetrad, occurs

crossing over occurs

tetrad

2 chromosomes, each from a parent

metaphase 1

shortest phase

tetrads align on equatorial plate

independent assortment, chromosomes separating randomly to cause genetic recombination, occurs

anaphase 1

homologous chromosomes separate and move toward poles

sister chromatids remain attached to centromeres

telophase 1

each pole contains a haploid set of chromosomes

cytokinesis occurs and 2 haploid daughter cells are formed

meiosis 2

chromosomes separate into chromatids

very short

no dna replication nor interphase

prophase 2

nucleus and nucleolus disappear

chromosomes condense

spindle fiber forms

metaphase 2

chromosomes (not homologous) line up at equatorial plate

anaphase 2

sister chromatids separate and move to opposite poles

telophase 2

nuclei and nucleoli reform

spindle fiber disappears

cytokinesis occurs and 4 haploid daughter cells called gametes form

dna

double stranded

established by watson and crick, double helix discovered by rosalind franklin

codes for genes

made with nucleotides

located in the nucleus

parts of a nucleotide

phosphate (circle)

sugar-deoxyribose or ribose (pentagon)

nitrogenous base (rectangle)

double ring purines

adenine and guanine

single ring pyrimidines

thymine and cytosine

rna

monomer (building block) is nucleotides

carries message to the ribosomes

single stranded

located in nucleus and cytoplasm

dna replication

happens during s phase

begin at origin of replication

two strands separate to form a replication fork where dna strands are elongating

helicase unwinds dna, rna primase adds primer to start replication, dna polymerase adds nucleotides

karyotype

organized picture of chromosomes from a human arranged from largest to smallest

1-22 are autosomes and last pair are sex chromosomes

nondisjunction

chromosomes fail to separate, thus causing gametes to have too few or too many chromosomes

down syndrome

trisomy 21

abnormal facial features, short stature, heart defects, degree of intellectual disability

klinefelter syndrome

xxy or xyy

male sex organs, sterile, feminine body characteristics

turner syndrome

monosomy x

only viable monosomy in humans

lack of sexual maturity and sterility, short stature

transcription

occurs in nucleus

dna segment unwinds and dna copies to mrna

rna polymerase joins rna nucleotides so mrna codons are complementary to triplet code in dna

rna processing

occurs in nucleus

exons code for proteins

introns are spliced out and exons rejoin

translation

protein synthesis

occurs in cytoplasm at the ribosome

trna molecules bring amino acids from cytoplasm to mrna