General Biology Unit 2 NWMSU

Ability of an organism

•Grow

•Replace old or damaged cells

•Reproduce sexually

Cell Division

Carries out cells abilities

Part of cell cycle

Life cycle of the cell

Cell Cycle

1. Interphase

2. Mitosis

3. Cytokinesis

Interphase

Longest stage: G1, S, and G2 stage

G1 stage

normal cell metabolism, controls rate of cell divis, varies significantly in duration from minutes to hundreds of years

S stage

synthesis of DNA, chromosomes replicate and centrioles replicate and begin to move toward opposite poles

G2 stage

Prepares for mitosis

G2 and S stage

do not vary much in duration

Chromosome structure

DNA + complex histones

Chromatid

one of two identical "sister" parts of a duplicated chromosome

Kinetochore

Protein complex around centromere

Centromere

Region of a chromosome where the two sister chromatids attach

Sister chromatids

one of two identical halves of a replicated chromosome

genetically related to one another

Kinetochore microtubules

spindle microtubules that attach to the kinetochores and push and pull them around

Mitosis

•Refers specifically to event is the nucleus

•Does not refer to cell division

•Occurs in somatic cell (body cells)

•Involve one nuclear division

•One diploid (2n) mother cell gives rise to 2 diploid daughter cells

Diploid

Double set of chromosomes

Most organisms, like humans, are this 23*2=46

46

Chromosome number for humans

Mitosis process

1. Prophase

2. Metaphase

3. Anaphase

4. Telophase

Prophase

•Chromo begin to condense

•Spindle fibers or spindle apparatus (MT) begin to form

Metaphase

•Chromo completely condensed

•Spindle MT have aligned chrom in center of cell

Anaphase

•Centromere of each chromo separates so that now, technically, there are two chromo; sister chromatids

•MT begin to depolymerize pulling chromo toward opposite poles

Telophase

•Spindle MT begin to disappear

•Chromo begin to unravel

•Nuclear membrane begins to reform

•Once nuclear membrane formed, telophase over

Cytokinesis

Typically, but not always, occurs at same time as telophase forming two new nuclei so that you have two new cells each 2n

Cleavage furrow

The area of the cell membrane that pinches in and eventually separates the dividing cell in animal cells

Cell plate

In a plant cell, midline of dividing cells. Becomes the cell wall eventually.

Binary fission

a pinching in equal halves of a cell in prokaryotic cells

As the cell replicates its single chromosome, the copies move apart and the growing membrane then divides the cells

How Prokaryotic cells reproduce

asexually by cell division

Check points

control mechanisms in eukaryotic cells which ensure proper division of the cell.

Chemotherapy

targets cell cycle

Interferes with DNA replication, chromosome separation

Cancer drugs

Look to plants as a source of drugs

Taxol

Highly effective chemotherapy agent; extracted from the Pacific yew tree, Taxus brevifolia

Meiosis

• Refers specifically to event in the nucleus

• Does not refer to cell division

• Occurs in germ cells, ovaries and testes, formation of gametes

• Involved 2 nuclear divisions

• One diploid mother cell gives rise to haploid daughter cells

• DON'T EQUATE WITH CELL DIVISION

homologous

23 pairs of chromo

they are genetically related

Meiosis I

Starts out similar to mitosis

reduction division

Prophase I

Stage in Meiosis I

•Similar to prophase of mitosis

• Synapse (pair) of homologous chromosomes (generates the haploid condition)

• Here each homologous binds, gene-for-gene

• Crossing-over occurs producing recombinant chromatids (chromosomes), mixes parental genes, creates genetic variation

Synapse

Pair

homologous chromosomes

generates the haploid condition

a pair of chromosomes having the same gene sequences

Crossing-over

the exchange of genetic material between homologous chromosomes during meiosis

recombinant chromatids

Mixed parent genetics

Metaphase I

• Similar to mitosis, except that not all 46 chromo align, but rather the 23 homologous pairs

• Each homol pair align in the equator of the cell independent of all others= independent assortment

Create genetic variation in gametes

independent assortment

Each homol pair align in the equator of the cell independent of all others

Anaphase I

Stage in meiosis I

homologous chromosomes separate

Telophase I

Stage of meiosis I

chromosomes arrive at the spindle poles.

Cytokinesis I

Stage in Meiosis I

2 haploid cells, replicated

Prophase II thur Telophase II

• Similar to mitosis, except only half number of chromo

• No different than mitosis I but it's only half

Cytokinesis II

4 haploid cells are formed, not identical but similar

Evolutionary importance of the meiosis

lies in genetic variation produced by recombination

Sources of recombination

a. Crossing-over and production of recombinant chromatids

b. Independent assortment and rearrangement of chromosomes in gametes

c. Fertilization (recombining of gene sets) and production of viable, fertile individual

Chromosomes and Human Genetics

Most organisms sex is determined genetically

autosomes

Humans have 22 pairs of...

sex chromosomes

Humans have 1 pair of...

X and Y chromosomes

Each chromosome has its own characteristics of

size, length, centromere location

karyotype

A display of the chromosome pairs of a cell arranged by size and shape.

amniocentesis

routinely done for pregnant women over age 35 in procedure

chorionic villi sampling (CVS)

sampling of fetal tissue from the placenta

Has higher risk of abortion

XX

Female

XY

Male

Aneuploid of autosome

humans- 45 or 47

Monosomy

45 chromosomes usually lethal

Trisomy

• 47 most autosomal trisomy are lethal

• Could be trisomy 21 or down syndrome, can have mental, muscle, heart problems, nondisjunction of chromo #21

X0

Turner's Syndrome

Turner's Syndrome

a. Nondisjunction in sperm

b. People are females, w/o sex hormones

c. Short, infertile, reduced development of sexual characteristics

d. Monosomy--45

XXY

Klinefelter syndrome

Klinefelter Syndrome

a. Nondisjunction in egg 67% of the time

b. Males that tall and usually sterile due to reduced develop of testes

c. Little facial hair and some breast development

d. Trisomy 47

XYY

normal male

XXX

normal female

Variation

among individual or is a long noticed

pattern

resemblance between parents and offspring

blending inheritance (incorrect idea)

Offspring traits were a blend of mix of the parents

Gregor Mendel

• An Austrian monk

• Considered "Father of modern genetics"

segregation of alternative traits

He described process...

published in 1865

F1 generation

Mix of 2 traits

F2 Generation

selfening of F1). This allowed for alternative traits to segregate

reciprocal crosses

A process by which plants were crossed (mated with each other) in both directions.

monohybrid cross

A cross between individuals that involves one pair of contrasting traits

dominant trait

a trait that masks the expression of another trait

recessive trait

a genetic factor that is blocked by the presence of a dominant factor

Mendel's Law of Segregation

1. theory of blending inheritance is wrong

2. Traits are passed from one generation to another as discrete information Exactly how not known then

chromosomes

threadlike structures made of DNA molecules that contain the genes

alleles

Different forms of a gene

Every individual possess 2 doses for a particular trait or gene. If individual are diploid

anaphase I

When gametes form, alleles segregate from each other

Phenotypes

are expressions of genotypes or exact allelic combinations for particular trains

PP

homozygous dominant

pp

homozygous recessive

Pp

heterozygous individuals

Punnett Square

possible outcomes of a cross can be identified

dihybrid cross

following two traits at same time

A cross between individuals that have different alleles for the same gene

phenotypic ratio

3:1

Mendel's Law of Independent Assortment

the law that states that genes separate independently of one another in meiosis

metaphase I

Pairs of homologous chromosomes move to the equator of the cell.

sex-linked

Genes fond on the sex chromosomes are...

X-linked

A recessive trait determined by a gene most commonly found on the X chromosome

X-linked recessive inheritance

• Hemophilia A- blood clotting

• Duchene muscular dystrophy- muscle cells atrophy

• Red/green color blindness

Carrier

Has trait, but it's not expressed

X-Linked dominant inheritance

Faulty enamel trait, failure of enamel coating on teeth to develop

Here a heterozygous female will express the trait

Autosomal Recessive Disorder

• Cystic Fibrosis

• Common more among Caucasians in US

• Faculty channel protein (CFTR protein) normally when CI- passes thru, water does too

• Mutant protein fails to pass CI- ion

• Mucus in bronchial tubes and pancreatic ducts is thick

• Interferes with breathing and release of digestive enzymes, respectively

Autosomal Dominant Disorders

Huntington Disorder

Huntington Disorder

• Progressive degeneration of nervous system leading to poor muscle coordination and mental decline- usually not expressed until 40's

• Mutation of gene (huntingtin gene) coding for protein called huntingtin

• Usually not expressed until middle age

• Death 10-15 years after expressed

Incomplete dominance

the phenotype of the heterozygous phenotype is distant from and often intermediate to the phenotypes of the homozygous phenotypes

Ex hair texture

Codominance and Multiple Alleles

Phenotype are A, B, AB, O controlled by three alleles and produced by 6 different genotypes