T2: mitosis and meiosis

What makes up a DNA molecule

Phosphate group, sugar, and nitrogenous base

Purines

2 rings (A and G)

Pyrimidines

1 ring (T and C)

what bond is between nucleotides to join sugar to phosphate

phosphodiester linkage

what do these phosphodiester bonds create

a single-stranded DNA molecule

backbone

binded sugars and phosphates that hold the nucleotides together with bases sticking out

what do the bases encode for

encodes for genetic information

what is the bond between bases

hydrogen bonds

how many bonds between C-G

3 hydrogen bonds

how many bonds between A-T

2 hydrogen bonds

what does complementary mean (complementary base pairs)

does not mean the same it means the other base that can bond with it

shape of a double-stranded DNA molecule

it is not flat, it twists into a double-helix shape

what does the DNA double-helix wrap around

histone protein

chromosome

DNA double-helix plus its proteins

how many chromosomes does human cells contain

46

what is a chromosome made out of

one long DNA double-helix

where do u find specific genes on chromosomes

specific locations on DNA molecule

gene

region on DNA that encodes info for making a specific protein or functional RNA

how many genes do chormosomes contain

can contain MANY genes

unfertilized human egg cell (chromosomes)

• contains 23 different chromosomes

• each chromosome have different set of genes

genome

a complete set of genes

how to make one complete genome

have all 23 chromosomes

what happens when we fertilize the egg?

egg with whole genome (n=23) and sperm (n=23) so the fertilized egg will have 2 complete genome

how many chromosomes does the zygote have

2n=46

haploid

cells with 1 genome

• e.g. gametes (egg/sperm)

diploid

cells with 2 genomes

• e.g. somatic cells (non sex cells)

homologous chromosomes

have the same set of genes at the same loci but have different genes

allele

one particular version of a gene

3 events that introduce variation among siblings

1. independent assortments of chromosomes

2. crossing over

3. random fertilization (sex is a random draw from both parents diverse gamete pool)

cell cycle steps

1. M phase (mitosis and cytokinesis)

2. G1 phase

3. S phase (DNA replication)

4. G2 phase

what stage does cell division occur

M phase (mitosis/meiosis & cytokinesis)

what makes up interphase

G1 phase, S phase, G2 phase

interphase

represents the rest of the cells life cycle

what happens during M phase

DNA is tightly coiled into chromosomes and no access for gene expression

what happens during interphase

chromosomes loosen into relaxed mass of chromatin and gene expression can resume

1. some cells stop actively dividing and enter G0 phase and just do their jobs

2. preparation for next M-phase (G1, S, G2)

G1 phase

the cell grows and makes more cytoplasm

S phase

DNA replication copies all nuclear DNA

G2 phase

the cell grows and makes more cytoplasm

is interphase apart of mitosis

No, DNA is just replicated in the S phase

early mitotic prophase

• chromosomes condense

• coiling up, becoming visible

late mitotic prophase

• nuclear envelope breaks down (has more space to move things)

• mitotic spindle forms and spindle fibers attach to each chromosomes centromere

mitotic metaphase

• mitotic spindle is fully formed

• each replicated chromosomes is lined up individually, across the metaphase plate

• are preparing to separate

mitotic anaphase

• each pair of sister chromatid separate and pulled to opposite sides of the cell along kinetochore microtubules

• non-kinetochore microtubules push apart to elongate cell and further separate chromosomes

mitotic telophase

• chromosome uncoil

• nuclear envelop reforms as spindles dispersed

• cytookinesis separates cell by forming a cell plate or cleavage furrow

prophase I

• chromosomes coil up and nuclear envelop breaks down

• each chromososme synapses with its homologue forming a tetrad

• spindle fibres attach to both sides of each tetrad, so each chromosomes centromere is attached to only one spindle fibre

chiasmata

the X-shaped points of contact where homologous (non-sister) chromatids physically overlap.

metaphase I

• spindle is fully formed

• each replicated chromosomes lines up with its homologue across metaphase plate as a tetrad

anaphase I

• each pair of homologous chromosomes seperate

• each replicated homolgue is pulled to opposite sides of the cell along kinetochroe microtubules and non-kinetochore elongate the cell

telophase I and cytokinesis

• chromosomes uncoil, the nuclear envelope reforms

• spindles dispersed

• cytokinesis separates cell by forming cell plate or cleavage furrow

what happens after telophase I (between meiosis I and II)

a brief interphase also known as interkinesis

• no DNA replication occurs

prophase II

• chromosomes coil up

• nuclear envelope breaks down

• spindle fibers attach to both sides of each chromosomes

• (tetrads are not formed bc no homologues to synapse with)

• n=2

metaphase II

meitotic spindle is fully formed

• each replicated chromosome lines up individually across metaphase plate

anaphase II

• each pair of sister chromatids separate and puled to opposite sides along kinetochore microtubules

• non-kinetochore microtubules elongate the cell and further separate the chromosomes

telophase II & cytokinesis

• chromosomes uncoil

• nuclear envelope reforms

• cytokinesis separates the cells by formng a cell plate or cleavage furrow