1. Heredity and Genetic Mutations
Saturday, December 01, 2018

2. Description Example Codominance
Incomplete Dominance
One allele is not completely dominant over another
Mirabilis plant: a red plant is crossed with a white plant, producing heterozygous pink plants
Codominance
Both alleles contribute to the phenotype.
One variety of chicken: a black-feathered chicken, producing heterozygous speckled chickens.
Multiple Alleles
A gene has more than one allele.
Human blood type: The alleles are A and B (which are codominant) and O.
Polygenic Traits
Traits are controlled by more than one gene.
Human skin color: More than four different genes control this trait, leading to a wide range of colors.

3. Incomplete Dominance

4. Codominance

5. Multiple Alleles

6. Polygenic Traits

7. Mutations
Mutation ( mutare “to change”)—changes in the DNA sequence that affect genetic information like inserting an incorrect base or skipping a base
Gene mutations
Chromosomal mutations

8. Gene Mutations Result from changes in a single gene
1. Point mutations are mutations that affect one nucleotide (sugar, phosphate, nitrogen base) and they occur at a single point in the DNA sequence
Ex. Substitute one nucleotide for another
Generally change one amino acid in a protein

9. Gene Mutations
2. Frameshift mutations occur when a nucleotide is inserted or deleted and the reading frame of the genetic message is now shifted since the genetic code is read in groups of three bases known as codons
Affects every amino acid that follows the point of insertion or deletion.
Mutations can alter a protein so it’s unable to perform a function

10. Chromosomal Mutations

11. Chromosomal Mutations
Chromosomal mutations involve changes in the number or structure of chromosomes
Deletion—loss of all or part of a chromosome.
Duplication—a segment of a chromosome is repeated.
Inversion—when part of a chromosome is oriented in the reverse of its usual direction.
Translocation—part of one chromosome breaks off and attaches to another, nonhomologous chromosome.
Usually, two translocations occur at the same time

12. Chromosome Disorders
If a sperm or egg cell gets fewer or more chromosomes than normal, this can cause genetic disease.

13. Down’s Syndrome These persons have three copies of chromosome #21.
They can be shorter, have learning disabilities and heart problems.

14. Down’s Syndrome
Sperm ? DD
Fetus Dies
DDD D_ D
DDD D_ D
Eggs

15. Non-disjunction When chromosomes fail to separate.
One sex cell gets an extra chromosome.
One sex cell doesn’t get a chromosome.

17. Recessive Genetic Disorders
Offspring only gets the disease if he/she inherits the recessive alleles from mom and dad.

18. Cystic Fibrosis
Causes a thick fluid to build up in the lungs, making it difficult to breathe.
Cystic Fibrosis is a Recessive Genetic Disorder.

19. Carriers
Mom and dad are carriers- They carry the defective allele, but don’t have the disease.

21. Sperm c C
Cystic Fibrosis CC Cc C Cc cc c
Eggs

22. Sex Determination Females have XX chromosomes.
Males have XY chromosomes.

23. Girls
Sperm Y X
Boys XX XY X XX XY X
Eggs

24. Sex-Linked Disorders An allele inherited on a sex chromosome.
Color blindness is an example.