Bio Unit 6 - Cell Division and the Reproductive System

why are cells small?

more efficient: surface area to volume ratio

how do cells stay small while the organism grows?

division

where does asexual reproduction occur?

in single celled organisms (bacteria, some simple animals/plants)

What is asexual reproduction?

The production of genetically identical offspring from a single parent

What is sexual reproduction?

Reproduction involving 2 parent organisms combining genetic material to create diverse offspring.

what are the advantages of sexual reproduction?

genetic diversity

why do cells divide?

growth, repair, reproduction

prokaryotic divison

binary fission

eukaryotic division

mitosis and meiosis

Prokaryote chromosome structure

single circular chromosome

eukaryotic chromosome structure

multiple and linear

histones

supporting proteins that help organize DNA

nucleosomes

DNA coiled around histones

How many chromosomes do humans have?

46

what is mitosis for

cell growth and repair

interphase

g1, s, g2

G1 phase

Cell growth

S phase

DNA replication (synthesis)

G2 phase

prepares for mitosis

M phase

mitosis and cytokinesis

phases of mitosis

prophase, metaphase, anaphase, telophase

what happens during prophase

chromosomes condense, nuclear envelope disappears, spindle forms

what happens during metaphase

Chromosomes line up in the middle of the cell

what happens during anaphase

sister chromatids separate and move along spindle fibers to opposite ends of the cell

what happens during telophase

spindle disappears, nuclear envelope forms

what happens during cytokenesis

cytoplasm divides; 2 new daughter cells

products of mitosis

two identical daughter cells (somatic cells)

Where is the G1 checkpoint?

end of G1

what happens at the G1 checkpoint

cells enter G0 unless there is a signal to divide (growth factor)

Where is the G2 checkpoint?

At the end of the G2 phase, before the start of the mitotic phase

what happens at the G2 checkpoint

The cell checks that the DNA has replicated, then enters M phase if MPF is present

Where is the M checkpoint

between metaphase and anaphase

what happens at the M checkpoint

cells enter anaphase when all chromosomes are attached to the spindle

what are cyclins

proteins that regulate the cell cycle

when are cyclins produced

during G2 phase

what is cdk

cyclin dependent kinase

where is cdk present

throughout the whole cell cycle

what is MPF

combination of cdk and cyclin

what does MPF do

triggers a cell's passage past the G2 checkpoint into the M phase (starts mitosis)

what is cancer

uncontrolled cell growth

what is meiosis

cell division that produces gametes for sexual reproduction

what does meiosis result in

4 haploid cells

what is the goal of crossing over

genetic diversity

what happens in prophase I

same as prophase, homologous pairs form tetrads, crossing over

what happens in metaphase I

Paired homologous chromosomes line up across the center of the cell

what happens in anaphase I

Homologous chromosomes separate, sister chromatids stay together

what happens in telophase I

2 nuclear envelopes form, chromosomes decondense, spindle disassembles

what happens in meiosis II

similar to mitosis (sister chromatids separate)

what is the end result of meiosis 2

4 haploid cells

what is the difference between male gametogenesis and female gametogenesis

male = 4 sperm cells, female = 1 large egg cell (unequal division of cytoplasm)

what are gametes

reproductive cells (sperm and egg)

what are gonads

organisms that produce gametes (ovaries and testes)

what is the sexual reproduction process

1. produce gametes, 2. gametes fuse to form zygote, 3. zygote undergoes mitosis and develops into a baby

testes

produces sperm and testosterone

scrotum

holds testes away from body to reduce temperature

Epididymis

location where sperm mature

vas deferens

tube that carries sperm from the epididymis to the urethra

prostate gland

A gland in males that contributes to the seminal fluid.

ovaries

produce egg cells and estrogen

fallopian tubes

where fertilization takes place, connects ovaries to uterus

uterus

supports growth and development of a fetus

cervix

The opening to the uterus

vagina

connects the uterus to the outside of the body

what do FSH and LH do

stimulate the gonads to produce sex hormones

where are FSH and LH produced

from the brain

steps of fertilization

1. sperm and egg meet in fallopian tube, forming a zygote 2. zygote is a diploid that goes through mitosis 3. embryo forms

what is an embryo

small ball of rapidly dividing cells

what is the placenta

connects maternal and fetal systems

where does the fetus develop

in the uterus

what happens during the first trimester

most dramatic change, body takes shape and organs form

what happens during the second trimester

growth and definement

what happens during the third trimester

period of primary growth