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Genetics II Study Guide
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1. Carrier - Only females can be carriers of recessive sex-linked disorders. Carriers
are heterozygous for sex linked disorders and DO NOT have the disorder but can
pass it on to offspring
2. Autosome - chromosome with genes not related to sex of organism (body cells)
3. Female chromosomes – XX
4. Male Chromosomes – XY
5. Determines sex of child - father
6. Y chromosome - male characteristics, Y chromosome is much smaller and has
genes only for sex determination
7. Why are males more likely to than females to have genetic disorders? All sexlinked genes are expressed, even recessive. Females have a backup X
chromosome.. Sex linked genes are NEVER on the Y chromosome.
8. Can female have a recessive sex linked trait – yes, if she has 2 recessive alleles
Example: XcXc – female will be colorblind
9. Incomplete dominance - when neither gene is totally dominant to the other,
Examples: White flowers and red flowers produce pink flowers, straight and curly
hair produce wavy hair
10. Sickle Cell Anemia - RR = normal blood
RR’ = some sickle cells, some normal cells
R’R’ = has sickle cell anemia
11. Codominant - alleles will both be completely expressed.
12. Number of alleles that determine blood type – 3
13. Genes for blood types:
Blood type
A
B
AB
O
Genes
IA IA or IA i
IBIB or IBi
IA IB
ii
14. Polygenic traits - are produced by interaction of two or more genes. Example:
eye color, height
15. Epistatic gene - can interfere with the expression of all other genes. Epistatic
gene will be expressed
16. How phenotype is expressed - is a combination of genotype and
environment.
.
17. Cross-over frequencies and map units – add up both distances
18. Amniocentesis – used to test skins cells of unborn baby. Method to check
chromosomes
19. Pedigree - chart for tracing genes in a family
20. Karyotype - a picture of all chromosomes in a cell can show changes in
chromosomes. Can be used to identify Down’s syndrome
21. Hemophilia – sex-linked recessive disorder in which blood does not clot properly
Understand:

Lab 27.2 – Punnett squares for hemophilia

How to read a pedigree chart