bio 111 - exam 4

binary fission -

how bacteria reproduce (asexual, make clones)

DNA is made up of

one circular chromosome

describe binary fission

a form of asexual reproduction where a single cell divides into two identical daughter cells

what proteins helps in binary fission

FtsZ protein

eukaryotes have

linear chromosomes

humans have _ chromosomes

46 chromosomes, 23 pairs

chromatin =

DNA + proteins, 40% DNA 60% proteins

chromosomes are made of

chromatin

heterochromatin =

inactive

euchromatin =

active (used for making stuff)

DNA wraps around - to make _

histones, nucleosomes (like beads on a string)

in mitosis, chromatin coils tightly using _ proteins

condensin

karyotype -

picture of chromosomes lined up by size and shape

diploid -

2n, 2 sets one from each parent

haploid -

n, 1 set

homologous chromosomes -

same kind, one from each parent

sister chromatids -

exact DNA copies joined at the centromere by cohesion

Eukaryotic cell cycle

G1: cell grows, makes proteins (longest phase)

S: DNA gets copied (synthesized)

G2: cell gets ready to divide - organelles copied, spindle starts to form

M phase: mitosis (nucleus splits)

Cytokinesis: cell splits into 2

Interphase: G1 + S + G2 (cell is busy getting ready)

G0 phase: resting phase (some cells like nerves stay here forever)

Interphase

G1: cell is active, growing, making stuff

S: DNA replication

G2: chromosomes condense slightly, centrosomes/centrioles copy, microtubules (spindle fibers) start to form

centromere -

where sister chromatids are connected

kinetochore -

protein at centromere that connects to microtubules

what are the stages of mitosis

PMAT - prophase, prometaphase, metaphase, anaphase, telophase

describe to prophase stage of mitosis

chromosomes condense, spindle fibers form, nuclear envelope starts to break, in animal cells: centrioles move apart, asters form

describe the prometaphase stage of mitosis

nuclear envelope disappears, microtubules attach to kinetochores, chromosomes start to move

describe the metaphase stage of mitosis

chromosomes line up in the middle (metaphase plate)

describe the anaphase stage of mitosis

sister chromatids separate, pulled to opposite sides, 2 types of movement: anaphase A - chromatids move anaphase B - poles move apart

describe the telophase stage of mitosis

chromosomes uncoil, nuclear envelopes form again, nucleolus comes back, mitosis is done

describe cytokinesis

cell splits, animals - cleavage furrow forms (uses actin) plants - cell plate forms from vesicles (becomes new cell wall) fungi/protists - nucleus divides inside an envelope (mitosis inside the nucleus)

cell cycle has checkpoints to control division what are they

G1/S checkpoints, G2/M checkpoint, spindle checkpoint (during mitosis)

describe the G1/S cell cycle checkpoint

cell decides if its ready to copy DNA, checks for size, nutrients, DNA damage, growth signals, once it passes this it usually finished the whole cycle

describe the G2/M cell cycle checkpoint

checks in DNA is fully copied, DNA has no damage, if OK cell starts mitosis

describe the spindle checkpoint cell cycle checkpoint

during mitosis, checks if all chromosomes are attached to spindle fibers before separating

two types of control proteins are

cdks (cyclin dependent kinases) - enzymes that drive the cycle

cyclins - proteins that activate cdks

cdk + cyclin =

active complex

active complex does what

helps cell move through checkpoints

cancer -

uncontrolled cell division

what are some signals that regulate growth

growth factors (proteins from outside the cell), PDGF (platelet-derived growth factor) tells cells to divide when healing

proto-oncogenes -

normal genes that help cells grow, if mutated become oncogenes (can cause cancer by overstimulating division)

tumor suppressor genes -

stop cell division or fix problems, if mutated cell doesn’t stop when it should. p53 is the most important one

p53 -

tumor suppressor gene, checks for DNA damage, tries to fix it, if it can’t fix it causes cell death (apoptosis)

missing or broken p53 is found in _ of cancers

50%+

sexual life cycle =

meiosis + fertilization

diploid (2n) =

somatic cells (2 chromosome sets)

haploid (n) =

gametes (1 chromosome set)

somatic cells:

diploid —> divide by mitosis

germ-line cells:

diploid —> divide by meiosis to make gametes

XX =

female

XY =

male

variations of chromosome based gender

XO (turner), XXX, XXY (klinefelter), XYY, XXYY

intersex -

individuals with variations in gonads, genitals, hormones, or chromosomes

meiosis =

2 divisions, meiosis I and II, each with PMAT stages

synapsis -

homologous chromosomes pair up during prophase I - forms tetrads (bivalents)

describe crossing over

exchange of genetic material between non-sister chromatids, creates genetic diversity, occurs at chiasmata and is complete before metaphase I

unique features of meiosis

meiosis I = reduction division (diploid —> haploid), no DNA replication between divisions, meiosis II = like mitosis (separates sister chromatids)

what are the stages of meiosis

1. prophase

2. metaphase

3. anaphase

4. telophase

describe prophase I in meiosis I

chromosomes condense, nuclear envelope dissolves, synapsis + crossing over —> tetrads form

describe metaphase I in meiosis I

homologous pairs align randomly at metaphase plate, monopolar attachment: both sister chromatids attach to same spindle pole

describe anaphase I in meiosis I

homologs pulled apart (sister chromatids stay together), independent assortment of maternal/paternal chromosomes

describe telophase I in meiosis I

nuclear envelope may reform, cells now haploids, but with sister chromatids still joined

describe prophase II in meiosis II

new spindle forms

describe metaphase II in meiosis II

chromosomes align at metaphase plate

describe anaphase II in meiosis II

sister chromatids pulled apart

describe telophase II in meiosis II

4 haploid cells form

end result of meiosis

4 haploid gametes, in animals: become gametes directly, in plants/fungi: may divide again by mitosis

errors in meiosis

nondisjunction: chromosomes fail to separate —> aneuploidy, leads to miscarriages

ovarian menstrual cycle phases

follicular, ovulation, luteal

uterine menstrual cycle phases

proliferative, secretory

oogensis -

one primary oocyte —> 1 viable egg + 3 polar bodies (unequal division)

at birth females have _ follicles

1 million, each has a primary oocyte, arrested in prophase I

spermatogenesis stages:

spermatogonium → mitosis —> primary spermatocyte (2n). meiosis I —> 2 secondary spermatocytes (n). meiosis II —> 4 spermatids (n)

a healthy adult male produces _ sperm/day

100-200 million

how many STIs spread primarily via sexual activity

25+

how many cases per year in US of STIs

15 million

monohybrid cross -

1 trait with 2 versions (tall vs short)

mendels conclusions about heredity:

traits are discrete, one dominant one recessive, traits segregate during reproduction, recessive traits not lost, just hidden in F1

five element model

1. traits = discrete factors (genes)

2. each individual gets 2 alleles (one from each parent)

3. alleles can differ (homozygous or heterozygous)

4. alleles don’t blend

5. dominant expressed; recessive hidden unless homozygous

genotype -

genetic makeup

phenotype -

physical trait

principle of segregation -

1st mendelian law, alleles separate during gamete formation, fertilization = alleles reunited, linked to meiosis (even though mendel didn’t know it yet)

pedigree analysis shows _ in families

inheritance

principle of independent assortment -

2nd mendelian law, genes assorted independently if on different chromosomes, caused by random chromosome alignment during meiosis I

dihybrid crosses -

examines 2 traits at once (shape and color), RRYY x rryy —> F1: RrYy, F1 self fertilize —> F2 = 9:3:3:1 phenotype ratio, traits inherited independently

rule of addition (“or”) -

used for mutually exclusive events

rule of multiplication (“and”) -

used for independent events