mitosis and meiosis

Cell cycle consists of

interphase and mitosis

interphase

growth and development of the cell

mitosis

cell division

cell spends most of it’s life in…

interphase because there are three stages

3 stages of interphase

G1, S, G2

G1

growth of the cell

S

synthesis - DNA gets copied

more detailed synthase phase

DNA (chromosomes) are duplicated into sister chromatids

G2

more growth to prepare for cell division

checkpoints in the cell cycle \*purpose?

Where proteins regulate the cell cycle & check that all is normal

Chromosomes

a complex of tightly coiled DNA and protein

accurate representation: )(

Genome

an entire set of DNA for a cell

products of mitosis

2 identical daughter cells

main goals of mitosis (2)

growth of the organism, repair/replace damaged and old cells

types of cells that undergo mitosis

body cells (somatic) in animals, plant cells

simple version of mitosis steps

1. chromosomes are copied to form sister chromatids
2. sister chromatids separate to opposite sides of the cell
3. the cell divides and 2 identical daughter cells are formed

steps of mitosis

interphase, prophase, metaphase, anaphase, telophase, cytokinesis

interphase

cell grows, copies DNA, prepares for cell division, and centrioles form

state of DNA in interphase

in the form of chromatin

Chromatin

"loosened up”, uncoiled form of DNA

accurate representation: \~\~\~\~

Prophase

Chromosomes coil (become visible), nucleus begins to break down, centrioles move to opposite ends of cell and produce spindle fibers

Chromosomes

coiled DNA

Accurate representation: (

centrioles

organelle that forms the spindle fibers

spindle fibers

fibers that attach to sister chromatids (to pull them apart)

Metaphase

sister chromatids attach to spindle fibers at the centromere, sis chromatids line up in the middle of cell

sister chromatids

pairs of chromosomes that have been copied __and joined together__

accurate representation: ))((

\*different from chromatids

Chromatids

chromosome and its copy UNCOMBINED

centromere

region of chromosomes where spindle fibers attach to sis chromatids

Anaphase

sis chromatids are pulled towards opposite ends of cell by spindle fibers

accurate representation: )) --------- ((

(------ = spindle fiber)

Telophase

Chromosomes are on opposite ends, spindle fibers break down, nucleus forms around chromosomes, and chromosomes uncoil back into chromatin

cytokinesis

Division in cytoplasm - produces identical daughter cells

What is DNA

a sequence of nucleic acids with instructions for making proteins

nucleic acid pairings

Adenine (A) with Thymine (T)

Guanine (G) with Cytosine (C)

A goes with ..

T

G goes with..

C

Gene

a sequence of DNA that contains the instructions for a single protein

Allele

different variations or versions of the same gene

different DNA sequences mean

different alleles → different look/appearance

when an organism inherits 2 copies of each chromosome it inherits

2 copies of each gene and 2 copies of each allele

cells that go through meiosis

reproductive cells

human somatic cells have

46 chromosomes

haploid cell

cell containing half the number of chromosomes of an organism

diploid cell

cell containing 2 sets of chromosomes

fertilization

egg cell and sperm cell combining to form a zygote

gametes

egg and sperm cells

zygote

joint gametes (first cell of new organism)

example of haploid cell

gametes

example of diploid cell

somatic cells

meiosis

process of cell division that produces gametes

characteristics of meiosis

1. all cells go through 2 divisions
2. 4 daughter cells are produced
3. daughter cells are not identical to parent cells
4. daughter cells have half the amount of parent cell dna

Homologous chromosomes

chromosomes that have the same genes in the same locations and are the same size

2 genes - 1 mom, 1 dad

Meiosis 1 stages

prophase 1 w/ special event, crossing over, metaphase 1, anaphase 1, telophase 1, cytokinesis 1

prophase 1

dna coils into chromosomes, nucleus starts to break down, centrioles form spindle fibers

\*important because same as mitosis

special event

homologous chromosomes pair up, pairs are crammed in nucleus of cell

Crossing over

randomized swapping of portions of chromosomes (DNA) during prophase 1

what allows crossing over to occur

close proximity of homologous chromosomes

what happens after the crossing over phase

chromosomes look different - allows for genetic diversity

metaphase 1

spindle fibers attach to centromere, homologous chromosome pairs line up in middle of cell

Anaphase 1

homologous chromosomes are pulled away from each other - opposite ends of cell

\*pairs are separated

telophase 1

chromosomes uncoil, nucleus forms

Cytokinesis 1

cytoplasm divides = 2 __haploid__ daughter cells - not identical

steps of meiosis 2

Prophase 2, metaphase 2, anaphase 2, telophase 2, and cytokinesis 2

\*same steps and results **(except cytokinesis 2)** as meiosis 1 except happening to 2 cells simultaneously

prophase 2

dna condenses, nucleus breaks, spindle fibers form

metaphase 2

spindle fibers attach to centromeres, chromatids line up in middle of cell

Anaphase 2

chromosomes are pulled away from each other bc of spindle fibers - opposite ends of the cell

telophase 2

chromosomes uncoil, nucleus forms

Cytokinesis 2

cytoplasm splits = 4 haploid daughter cells __not identical__

what do capital and lowercase letters represent on genes

alleles

genotype

genetic makeup of a gene (2 alleles)

capital letter

dominant allele

lower case letter

recessive allele

when dominant allele is present in genotype

1. it gets written first ex. Aa
2. it __always__ expresses dominant allele

possible allele combos

AA, aa, Aa

AA

homozygous dominant (purebred)

aa

homozygous recessive (purebred)

Aa

heterozygous (hybrid)

what do genotypes determine

phenotypes

phenotypes

physical trait that is expressed (what we see)

when homozygous dominant

dominant trait expressed

when homozygous recessive

recessive trait expressed

when heterozygous

dominant trait expressed

Autosome

any chromosome that isn’t a sex chromosome

Sex chromosomes

determines an organism’s biological sex

karyotype

map showing all of an organism’s chromosomes

which pairs on karyotypes are autosomes

pairs 1-22

which pairs on karyotypes are sex chromosomes

pair 23

types of sex chromosomes

x and y

cell that carries only x

egg cells

cell that carries x or y

sperm cell

what determines sex of a child

chromosome carried by the sperm cell (x or y)

What is an autosomal genetic disorder

an inherited genetic disorder due to a genetic mutation on an autosome

sex-linked genetic disorder

an inherited genetic disorder due to genetic mutation on the x or y chromosome

what are sex linked traits

traits located on the sex chromosomes

what is the most common sex-linked trait

x-linked (carried on the x)

why are x-linked traits more common

because the x chromosome is larger than the y chromosome

which allele is written uppercase

dominant allele

which allele is written lowercase

recessive allele

what is the genotype for 2 dominant allele

homozygous dominant

what is the genotype for 2 recessive alleles

homozygous recessive

what is the genotype for 1 dominant and 1 recessive allele

heterozygous