1. Phenotype & Pedigrees

2. Human Genetics: Karyotypes
46 TOTAL
23 homologous pairs
46 TOTAL
Chromosomes
23 homologous pairs

3. What is the difference between an Autosome and a Sex-chromosome?
Autosomes are the first 22 homologous pairs of human chromosomes that do not influence the sex of an individual.
Sex Chromosomes are the 23rd pair of chromosomes that determine the sex of an individual.

4. Phenotype can depend on interactions of alleles.
In incomplete dominance, neither allele is completely dominant nor completely recessive.
Heterozygous phenotype is intermediate between the two homozygous phenotypes
Homozygous parental phenotypes not seen in F1 offspring

5. The environment interacts with genotype.
Phenotype is a combination of genotype and environment.
The sex of sea turtles depends on both genes and the environment
Height is an example of a phenotype strongly affected by the environment.

6. Linkage maps estimate distances between genes.
The closer together two genes are, the more likely they will be inherited together.
Cross-over frequencies are related to distances between genes.
Linkage maps show the relative locations of genes.

7. Gene Mapping
(9 min)

8. Cross-over frequencies can be converted into map units.
gene A and gene B cross over 6.0 percent of the time
gene B and gene C cross over 12.5 percent of the time
gene A and gene C cross over 18.5 percent of the time

9. Human genetics follows the patterns seen in other organisms.
The basic principles of genetics are the same in all sexually reproducing organisms.
Inheritance of many human traits is complex.
Single-gene traits are important in understanding human genetics.

10. A family history of a genetic condition
PEDIGREE CHARTS
A family history of a genetic condition
© 2007 Paul Billiet ODWS

11. Pedigree video

12. What is a pedigree chart?
Pedigree charts show a record of the family of an individual
They can be used to study the transmission of a hereditary condition
They are particularly useful when there are large families and a good family record over several generations.

13. Studying human genetics
You cannot make humans of different types breed together
Pedigree charts offer an ethical way of studying human genetics
Today genetic engineering has new tools to offer doctors studying genetic diseases
A genetic counsellor will still use pedigree charts to help determine the distribution of a disease in an affected family

14. Symbols used in pedigree charts
A marriage with five children, two daughters and three sons. The eldest son is affected by the condition.
Eldest child  Youngest child
Normal male
Affected male
Normal female
Affected female
Marriage

15. A pedigree is a chart for tracing genes in a family.
Phenotypes are used to infer genotypes on a pedigree.
Autosomal genes show different patterns on a pedigree than sex-linked genes.

16. If the phenotype is more common in males, the gene is likely sex-linked.

17. Organising the pedigree chart
A pedigree chart of a family showing 20 individuals

18. Organising the pedigree chart
Generations are identified by Roman numerals I II
III IV

19. Organising the pedigree chart
Individuals in each generation are identified by Arabic numerals numbered from the left
Therefore the affected individuals are II3, IV2 and IV3 I II
III IV

20. If the phenotype is more common in males, the gene is likely sex-linked.

21. Several methods help map human chromosomes.
A karyotype is a picture of all chromosomes in a cell.
X Y

22. Karyotypes can show changes in chromosomes.
deletion of part of a chromosome or loss of a chromosome
large changes in chromosomes
extra chromosomes or duplication of part of a chromosome

23. Incomplete Vs. Co-dominance
Codominance - A form of inheritance in which both alleles are equally shown.
Incomplete dominance - A form of inheritance in which the heterozygous alleles are both expressed, resulting in a combined phenotype.
Most commonly found in plants.
A red and a white allele gives pink. If it were codominance, you would see the red and white colors.

24. Codominant alleles will both be completely expressed.
Codominant alleles are neither dominant nor recessive.
The ABO blood types result from codominant alleles.
Many genes have more than two alleles.

25. Test Cross Used to determine an organisms genotype.
Either Bb or BB
Always a dominant unknown mated with pure recessive
B? X bb

26. Go to Page 188 in textbook Complete questions 1-4
Remember the genotypes you are using are:
Rrtt x RrTT resulting in Rt Rt rt rt x RT RT rT rT
RT rT
Rt RRTt RRTt
rt RrTt rrTt :1 ratio