Human Heredity How does a mutation occur?

A chromosome or specific gene is damaged.

If a mutation occurs in one of the gamete cells it’s called a germ cell mutation.

If a mutation takes place in a 2N cell it’s called a somatic mutation.

Most mutations decrease from 1 generation to the next.

It is truly a miracle to be born a healthy baby; everything has to form just right during mitosis.

4 main types of chromosome mutations 1. Deletion – is where a chromosome is

broken off so that all the information is lost. 2. Inversion - is where a chromosome piece

breaks off and reattaches the opposite way it was attached before it broke off.

3. Translocation – is where a broken piece of chromosome attaches itself to a different chromosome from which it was attached.

4. Nondisjuction – this is where a chromosome doesn’t separate right during cell division. One daughter cell receives 1 more chromosome than the other daughter cell.

What is a mutation? A sudden genetic change.

Examples of gene mutations: 1. A gene is not copied correctly 2. Chromosome problems 3. Environmental influence - radiation

What is a mutant? Organism showing a mutation

What is a mutagen? A substance that causes a mutation

An Ames test is used to identify mutagens.

What are some causes of mutations? Radiation from sun, x-rays, nuclear Smoke, chemicals, smog, etc.. Cancer

Thomas Morgan was a famous geneticist who studied fruit flies to determine the relationship between chromosomes and inheritance patterns.

Fruit flies were easy to study, since they only have 8 chromosomes.

Morgan discovered that all the female fruit flies had homologous chromosomes. XX-sex chromosomes.

He then figured out the males had a heterozygous chromosome (XY).

All the other chromosomes besides the sex chromosomes are called Autosomes.

Sex-linked traits are influence by the X of the sex chromosome. Remember males have 1 X & females have 2.

Morgan discovered that mainly male fruit flies had white eyes. This is a sex-linked trait.

F1 Gen. XRXR x XrY Homozygous Dominant X

Homozygous Recessive F2 Gen. XRXr x XRY

Applied Genetics The start of genetics and how it got started.

Hunters & gatherers were the 1st humans to use primitive genetics. Nomadic people of 20 to 50. Men hunted and the women gathered. About 10,000 to 12,000 years ago

Their nomadic lifestyle changed when the agricultural revolution started; this required to stay in one place.

Things that cause a genetic change 1. They started to domesticate crops – they

grew them instead of gathering them 2. Domesticated animals. 3. Build houses – no longer nomadic 4. The soil was starting to lose nutrients. 5. Waste was starting to build up Humans had to change crops and animals

genetically in order to stay in one place and provide enough food to stay in one place.

Applied genetics came along because of this change in lifestyle.

Applied genetics is the altering or controlling genetics to suit our needs. Control breeding for desired traits

Ex. Beef and grain production Mass selection is where the parents are

selected from a large number of possibilities .

Inbreeding is the mating of close relatives. Mutations may occur more

frequently. 20 to 30% of all albinos are produced

in marriages of relatives Hybridization is the crossing of 2

different, but similar organisms. Ex. Liger (tiger & lion), Beefalo

(buffalo & cow)

Hybrid vigor is having the best traits of both parents. Hybrids are usually sterile

(chromosomes are similar) Polyploidy is where an organism has

more than 1 complete set of chromosomes. Ex. Strawberries, tomatoes, wheat Ex. Wheat 14 to 28 to 42

chromosomes

Cloning – making exact copies of the parent organism. 1st done in plants. Now in sheep, mice, and possibly humans.

Genetic engineering – manipulating genes. Taking genes from one organism and putting them into another organism. Gene splicing – take a gene from 1

organism & put it in a DNA of another organism.

This comes from a plasmid (circular ring of DNA in bacteria).

Recombinant DNA – DNA segments from at least 2 different organisms.

Video Applications of Recombinant DNA 1. Insulin – made for diabetics 2. Interferon – protein produced by humans

to stop the reproduction of viruses. 3. Oil eating bacteria 4. Disease resistant plant crops Test tube baby – remove egg from mother

and fertilize with sperm of the father. Surrogate mother

Genetic Disorders A group of genes located on a chromosomes is a linkage

group. Video – genetic disorders Red-green color blindness is an example of a sex-linked

disorder in which the disorder occurs on the X chromosome. Occurs mainly in males. Why? Males only have 1 X, so they either carry it or don’t.

Genotypes: XCXC (normal), XCXc (carrier), XcXc (color blind female), XCY (normal), XcY (color blind male).

Video – Manipulating genes

Color-blindness occurs in 8% of males and about 1% of females.

Hemophilia (bleeders disease) – blood doesn’t clot properly. 1st discovered in Queen Victoria Inherited same as red-green color

blindness (sex-linked) 1 in every 10,000 born have

hemophilia These people lack factor VIII in their

blood, which helps clot the blood.

Sex influence traits are influenced by sex hormones produced by the individuals.

Ex. Baldness occurs more with the hormone testosterone.

Ex. Harelip (cleft palate) testosterone (males)

Ex. Spinalbifida estrogen (females)

Chromosomal Disorders Usually caused by nondisjunction –

a failure of chromosome pairs to separate properly during meiosis.

1. Monosomy – missing a chromosome (22 + 23 = 45)

2. Trisomy – one more chromosome (24 + 23 = 47)

Down Syndrome – caused by an extra chromosome on the 21st chromosome pair. Trisomy on the 21st chromosome pair 47 total chromosomes Occurs in about every 1 in 600 births

Turner’s Syndrome – a sex chromosome in a female is missing. Ex. XX – normal , X – Turner’s

Syndrome Undeveloped female

Kleifelter’s Syndrome – an extra X sex chromosome in males. Ex. XXY Poorly developed male

Jacobs’ Syndrome – an extra Y sex chromosome in males. Ex. XYY “Normal Male”

Amniocentesis is used by physicians to determine birth defects. They use a needle and syringe to remove some amniotic fluid from the mother’s amniotic sac that surrounds the fetus. Why is not used as much as

ultrasound? Ultrasound uses high-frequency sound

waves that bounce off the fetus to form an image.

Population sampling is where researchers use a small number of individuals to represent the whole population.

Gene pool – all the genes in a given population.

Gene frequency – the number of times a gene occurs in a population.

Types of Twins 1. Fraternal twins – develop from 2

fertilized eggs. Not identical – can get a boy and a girl Occurs in about 1 in every 100 births Most likely to occur in 35 – 40 year old

mothers. Tends to run in families

2. Identical twins – develop from a single fertilized egg. They have the same DNA

Other Genetic Disorders PKU (phenylketonuria) – a genetic disease

due to a “bad” gene (phenylalanine hydroxylase). This person is unable to produce a certain

enzyme. This causes damage to the nervous

system. Sickle-cell Anemia – genetic disease of

mainly blacks. Abnormal hemoglobin impairs the flow of oxygen to the body. 9% of U.S. blacks have this; 40% of

Africans have it.

Huntington Disease – occurs in a autosomal dominant alleles of a trait. Causes loss of muscle control

Cystic Fibrosis – most common lethal genetic disorder among white Americans. Have trouble digesting food and

breathing

Blood Types Antigens determine a person’s blood type

A, B, AB, O Video

Red blood cells are covered with an antigen Plasma is the liquid that contains an antibody which

reacts with antigens. Blood type antigens

1. Type A Ia Ia or Ia Io 2. Type B Ib Ib or Ib Io 3. Type AB Ia Ib 4. Type O Io Io

Type A can receive blood from A or O. It can donate to A or AB.

Type B can receive blood from B or O. It can donate to B or AB.

Type AB can receive from A, B, AB, or O (universal receiver). It can donate to AB

Type O can receive from O. It can donate to A, B, AB, or O (universal donor).

Mixing the wrong type of blood causes the cells to clump together or agglutinate.

Rh factor – protein found in RBCs Found 1st in the rhesus monkey 87% of white U.S. population has

the protein (+). 13% lack this protein (-).

Polygenetic trait – more than two genes determine the trait. Ex. Skin color – melanin (pigment

in skin) Albinism – no melanin P1P1 & P2P2 – darkest melanin P1p1 & P2p2 – medium melanin p1p1 & p2p2 – no melanin