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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.