HEREDITY

GENETICS

HEREDITY

• Heredity Is the passing of traits from parents to offspring.

• Genes on chromosomes control the traits that show up in an organism.

• The different forms of a traits that a gene may have are alleles.

Chromosome

CELL DIVISION

• During meiosis a pair of chromosomes separates and the alleles move into separate sex cells.

• Each sex cell now contains one allele for each trait.

• The study of how traits are inherited is genetics.

Mitosis

Meiosis

Gregor Mendel the father of Genetics

• Mendel was the first to use • mathematics of probability • to explain heredity and • to trace one trait for • several generations.• Hybrid receives different • genetic information for • a trait from each parent.

Mendel and Beans Experiment

ALLELES

• Dominant allele covers up or dominates the other.

• Recessive allele the trait seems to disappear.

• Probability helps you predict the chance that something will happen.

Dominant and Recessive Allele

GENETICS

• Punnet square can help you predict what an offspring will look like.

• Upper case letters stand for dominant alleles

• Lowercase letters stand for recessive alleles.

• Genotype the genetic make up of an organism.

Punnet Square

GENETICS

• Homozygous an organism with two alleles for one trait that are the same ( written TT)

• Heterozygous an organism with two alleles for one trait that are different ( written Tt)

• Phenotype the way an organism looks and behaves as a result of its genotype.

Phenotype

Genotype

Genetics since Mendel

• Incomplete dominance• Neither allele for a trait is dominant.• The phenotype produced is

intermediate between the two homozygous parents.

• Multiple alleles• More than two alleles that control a

trait are called multiple alleles.• Traits controlled by multiple alleles

produce more than three phenotypes.

Incomplete Dominance

Incomplete Dominance

Polygenic Inheritance

• A group of gene pairs acts together to produce a trait, which creates more variety in phenotypes.

• Many human traits are controlled by polygenic inheritance, such as hair and eye color.

Polygenic Inheritance

Polygenic Inheritance

MUTATIONS

• Mutations are genes that are altered or copied incorrectly.

• A mutation can be harmful, beneficial or have no effect.

• Chromosome disorders caused by more or fewer chromosomes than normal.

• Down’s syndrome caused by an extra copy of chromosome 21.

Normal Karyotype

Trisomy 21

Down Syndrome /Trisomy 21

Down Syndrome /Trisomy 21

Cleft Lip and Palate

Trisomy 18

Trisomy 18

Trisomy 18/Edwards Syndrome

Recessive Genetic Disorders

• Both parents have a recessive allele responsible for the disorder and pass it to their child.

• Because the parents are heterozygous, they don’t show any symptoms.

• Cystic Fibrosis is a homozygous recessive disorder.

Cystic Fibrosis

Cystic Fibrosis

Cystic Fibrosis

Hutchinson–Gilford Progeria Syndrome

CAUSE

• The gene LMNA encodes a protein called prelamin A.

• Prelamin A has a farnesyl group attached to its end. • Farnesyl group is removed from prelamin A. • Farnesyl group remains attached to prelamin A. • Normal form is called prelamin A.

• Abnormal form of prelamin A is called progerin. Prelamin A is not anchored to the nuclear rim.

• Progerin is anchored to the nuclear rim. Normal state of the nucleus. Abnormally shaped nucleus.

Sex Determination

• Chromosomes that determine the sex of an organism are XX in females and XY in males.

• Females produce eggs with an X chromosomes only. Males produce sperm with either an X or a Y chromosome.

Sex-linked disorders

• An allele inherited on an X or Y chromosome is a sex-linked gene.

• Color blindness is a sex- linked disorder caused by a recessive allele on the X chromosome.

• A pedigree follows a trait through generations of a family.

Advances in Genetics

• Genetic Engineering is changing the arrangement of DNA that makes up a gene.

• Recombinant DNA.• Insertion of a useful segment of DNA

into a bacterium.• Insulin is a made by genetically

engineered organisms.

Gene therapy

• A normal allele is placed into virus, which delivers the normal allele when it infects its target cell.

• May be used to control cystic fibrosis or other genetic disorders.

• Genetically engineered plants created by inserting the genes that produce desired traits in one plant into a different plant.

Sex- linked trait on the X chromosome is color

blindness Xc• Normal female• Normal male• Carrier female• Color-blind male

Sex-linked chromosome

Questionnaire

1. What is the genotype of the first generation female person 4 ?

• Xc X2. What is the genotype of the first

generation male, person 5 ? Xc Y3. What is the probability in percent of

person 6 passing on the color-blind trait ?

0 %

Questionnaire

8. What is the probability in percent of person 7 passing on the color-blind trait?

50 %9. Person 5 is color-blind. However, his

sons do not have this condition. What accounts for this?

Sons inherited only the Y chromosome from their father.