HEREDITY GENETICS HEREDITY Heredity Is the passing of

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 X 2. What is the genotype of the first generation male, person 5 ? Xc Y 3. 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.