Human Genetics

Human Genetic Map

http://www.hulu.com/watch/91438/ngc-presents-genetic-roadmaps

How many chromosomes are in a human sperm or egg?

23

How many chromosomes does a human have?

23 pairs

What is the total human chromosome number?

46

Do all animals have 23 chromosome pairs?

No, different species have different chromosome numbers and the number is not correlated to the complexity of the animal

How can you tell if a human child has the correct number of

chromosomes?

Amniocentesis – removal amniotic fluid to check chromosomal abnormalities

Chorionic villus SamplingDiagnosis chromosome abnormalities

Fetal Blood samplingCheck for genetic or chromosomal

abnormalities

Determination of sex

What are sex chromosomes?23 pair of chromosomes (X and Y)

How many sex chromosomes are there?2 –X chromosome and Y chromosome

How is your sex detemined?Female has 2 X chromosomes Male has 1 X and 1 Y chromosome

Determination of sex

How can you predict the expected sex of a child?By using a punnett squareA female can donate only an X chromosome A male can donate either a X or a Y

chromosomeWhat is the chance that the offspring will

be male or female?50 %

Other Facts about Chromosomes

Autosomes Other 44 body

chromosomes Sex Chromosomes

45 & 46 chromosomes Karyotype

A picture of chromosomes

Pedigree

Pedigree Chart Chart that shows the

relationship within a family

Used to study human inheritance patterns

Royal Family Pedigree

How do you read Pedigree Chart?

Who is the carrier for color-blindness?

Which parent is unaffected?

Which grandchild was the first to exhibit colorblindness and hemophilia?

How many children affected?

Royal Family Pedigree

Human Genetic Disorders

Genetic Disorders

Gene mutationsinherited from a

parent or acquired.

A hereditary mutation is a mistake that is present in the DNA of virtually all body cells.

Hereditary mutations (germ line mutations) the gene

change exists in the reproductive cells and can be passed from generation to generation, from parent to newborn.

Autosomal Disorders

Disorders involving the other 22 pairs of chromosomes.

Can result from an extra chromosome or defective genes

Autosomal Disorders Recessive Alleles

Disorders Albinism Cystic fibrosis Galactosemia Tay-Sachs Disease

Dominant Alleles Disorders Achondroplasia Huntington’s disease

Codominant Alleles Disorders Sickle cell disease

Recessive Autosomnal Disorders

Cystic Fibrosis A recessive disorder that

occurs in about 1 of 2,500 people of white European ancestry.

Mutation gene on chromosome 17.

Characterized by excessive secretion of the mucus in the body.

AlbinismPatients are unable to produce skin or eye

pigments, and thus are light-sensitive

Recessive Autosomnal Disorders

Tay-Sachs Disease Central nervous system

degrades, ultimately causing death.

Buildup of fatty deposit in brain & mental disability

Found in Chromosome 15 Common among people

of Jewish, eastern Europe descent.

Recessive Autosomnal Disorders

Galactosemia

1 in 50000-70000 affected Absent of gene that codes for

enzyme that break down galactose

Mental disabilities, enlarged liver, and kidney failure.

Monitor galactose intake

Recessive Autosomnal Disorders

Autosomal Disorders Dominant Alleles

Disorders Achondroplasia Huntington’s disease

Dominant Autosomal Disorders

Huntington Disease A dominant disorder that

occurs in about 1 of 10,000 people.

Chromosome 4 is responsible.

Causes degeneration of neurons producing dementia, and random jerking movements

Dominant Autosomal Disorders

Achondroplasia (Dwarfism) Has small body size and

limbs that is short No treatment

Mini-Me

Autosomal Disorders Codominant Alleles

Disorders Sickle cell disease

Codominant Autosomnal Disorders

Sickle-Cell Anemia Occurs in about

people with African descent

The defective gene on chromosome 11

Blood cell sickled on increase resistance Malaria

Sex Linkage (X-Linked) Disorders

If chromosomes are paired with other chromosomes with the same genes, what happens when you pair an X and Y chromosome?

Females have two forms of the same gene, just like on the rest of the chromosomes,

Men have only the form of the gene found on the X chromosome

If color blindness is a trait inherited on the X chromosome, why are

men more likely to be color blind?

The man doesn’t have a second X chromosome to keep recessive genes from being expressed

Sex-linked Disorders

Colorblindness Hemophilia

Sex-Linked Disorders

Hemophilia –Royal Family Disease

Recessive disorders that affect 1 of 5,000 males.

Interfere with normal blood clotting and occur at different loci on the X chromosome.

Sex-Linked Disorders

Color BlindnessGenetic X-linked

recessive disorder.Occurs in 1 of 10

males

Informal

colorblind

test

FIND A CIRCLE, SQUARE, and/or STAR

FIND CAR, BOAT, DOG, or BALLOON

Color BlindnessTest

Color Blindness

Chromosomal Autosomal Disorders

Down SyndromeExtra copy of chromosome at 21

Sex Chromosome DisordersTurner’s Syndrome

Only One X chromosome (XO)Klinefelter’s Syndrome

Extra X chromosome (XXY)

Chromosomal Autosomal Disorders

Down Syndrome Occurs in about 1 in

1,000 live births. An extra

chromosome is attached to the 21st pair.

Risk increases with pregnancies of women over age 35

Chromosomal Sex-Linked Disorders

Klinefelter Syndrome (XXY, XXXY, XXXXY)

Occurs in about 1 of 1,000 males.

Caused by an extra X chromosome

Some development of breast tissue, little body hair, small testes, infertility, and evidence of mental retardation may or may not be present.

Chromosomal Sex-linked Disorders

Turner’s Syndrome (XO)Occurs in about 1 of 10,000 females. One of the X chromosomes is either

missing or inactive. Women have immature female

appearance, do not develop secondary sex characteristics, and lack internal reproductive organs.

Hermaphrodite

An individual whose body contains tissue of both male and female gonads.

The ovaries and testes may be present as separate organs, or ovarian and testicular tissue may be combined in the same organ.

CausesAdrenal Gland imbalance during pregnancyMale hormone imbalance

The End