4.1-4.2: DNA, Mitosis and Meiosis

heredity

passing of traits from parents to offspring

trait

a specific characteristic or feature exhibited by an organim

traits are ____

encoded in genetic information inherited from parents

genetics

study of heredity and variation of inherited traits

DNA

deoxyribonucleic acid

RNA

ribonucleic acid

gene

distinct sequence of genetic information

genes are encoded by _____

a specific sequence of nucelotides

nucleotides

composed of a phosphate group, a sugar group, and a nitrogenous base

types of nucleotides

adenine, guanine, cytosine, thymine

purines (2 rings)

adenine and guanine

pyramidines (1 ring)

cytosine ad thyminec

what holds complementary base pairs together

hydrogen bonds

complementary base pairs

nitrogenous base pairs with another in a particular manner

thymine pairs with

adenine

cytosine pairs with

guanine

DNA strands are made of ___

nucleotides

phosphodiester bonds

join DNA strands

backbone of DNA strand

sugars and phosphate groups

“rungs” of DNA

nitrogenous bases

DNA strands run ____

antiparallel

base pairs are combined into sets

genes

gene sequences code for

unique proteins

function of proteins

work together to enable cells to function

chromatin

fibre of DNA wrapped around histones

chromatids

tightly wound chromatin

sister chromatid

genetically identical chromatids

chromosome

X-shaped condensed chromatids

centromere

connects chromatids

histone

proteins DNA wraps around

nucleosome

DNA and histone

homologous chromosomes

not genetically identical, code for the same trait

alleles

variations of the same genes

__ pairs of autosomes in humans

22

how many chromosomes do humans have

46

how many chromatids do humans have

23

the cell theory (1)

all living things are composed of one or more cellsthe

cell theory (2)

the cell is the smallest unit of living organismsc

cell theory (3)

new cells come only from pre-existing cells by cell division

purposes of cell division

growth, reproduction, repair

asexual reproduction

binary fission

sexual reproduction

requires fusion of two gametes, meiosis in humans

why do cells increase in number rather than size

if a cell is too big, entry and excretion of nutrients becomes inefficient

somatic cells

animal or plant cells that form the body of an organism

stages of the cell cycle

interphase, mitosis, cytokinesis

interphase

longest stage of the cell cycle, cell carries out normal functions, g1, S, and g2

G1

major period of cell growth, synthesizes new molecules in preparation for next phase

S

synthesis, DNA is replicated, appears as chromatin

G2

cell synthesizes more molecules before mitosis

cell cycle checkpoints

specialized proteins monitor cell growth and send messages to the nucleus

mitosis

goal is the accurate seperation of the cells replicated DNA, results in two genetically identical daughter cells

stages of mitosis

prophase, metaphase, anaphase, telophase

prophase

chromatin condenses into sister chromatids, nuclear membrane breaks down, centrosomes produce spindle fibres, spindle apparatus moves to opposite poles

metaphase

spindle fibres attach to centromeres, align on equatorial plate, nuclear membrane is dissolved

anaphase

centromeres split, daughter chromosomes are pulled towards opposite sides

telophase

daughter chromosomes stretch and become thin and invisible, nuclear membrane forms, cleavage furrow forms

cytokinesis in animal cells

cleavage furrow divides cytoplasm

cytokinesis in plant cells

cell plate forms between daughter nuclei

semi conservative replication

each new double stranded DNA is composed of the original and its copy

karyoypes

cell sample is stained to produce a banding pattern

how karyotypes are sorted

autosomes numbered 1-22, sex chromosomes labeled as X or Y

meiosis

division of gametes, produces a haploid number of chromosomes, diploid → haploid

haploid cells

1/2 the number of chromosomes as the parent, n chromosomes

diploid cells

same number of chromosomes as the parent, 2n chromosomes

fertilization

fusion of a male reproductive cell with a female reproductive cell, fusion of haploid gametes creates a diploid zygote

causes of genetic diversity in meiosis

crossing over and independent assortment

spermatogenesis

produces sperm

oogenesis

produces eggs/ova

prophase I

chromosomes condense, synapsis, crossing over

synapsis

homologous chromosomes align and form tetrads

crossing over

a section of a chromosome crosses over another and produce recombinant chromosomes

chiasmata

point where crossing over takes places

metaphase I

shortest phase, homologous pairs line up randomly of equator, independent assortment

independent assortment

chromosomes line up randomly in metaphase I and II

anaphase I

sister chromatids stay attached, half the total number of chromosomes pull to each pole

telophase I

nuclear membrane forms around each haploid cell, sister chromatids are already formed

meiosis II

purpose is to seperate sister chromatids, similar to mitosis, no interphase II

prophase II

same as mitosis

metaphase II

spindle fibres align chromosomes in single file along equatorial plate

anaphase II

sister chromatids are pulled to opposite cell poles

telophase II

nuclear membrane reforms around nuclei at poles

cytokinesis II

contractile ring pinches cells, results in 4 daughter gamete cells

when do eggs form

before birth until menopause

when do sperm form

from puberty until death

deletion

piece of a chromosome is deleted

duplication

a section of a chromosome appears two or more times in a row

inversion

a section of a chromsome is inverted

translocation

a segment of one chromsoome becomes attached to a different chromosome

non disjunction

when homologous pairs dont separate as they should

aneuploidy

too few or too many chromosomes

monosomy

loss of one chromosome

trisomy

extra chromosome

cri du chat

caused by deletion

charcot-marie-tooth disease

caused by duplication

FG syndrome

caused by inversion

cronic myelogenous leukemia

caused by translocation

down syndrome

trisomy 21

edward syndrome

trisomy 18

patau syndrome

trisomy 13

klinefelter syndrome

XXY