Download HEREDITY

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
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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
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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.