1. Inheritance Patterns and Human Genetics
Chapter 12
Inheritance Patterns and Human Genetics

2. Section 1 Vocabulary Pretest
Sex chromosomes
Autosomes
Sex-linked trait
Linked gene
Chromosome map
Map unit
Deletion
Inversion
Translocation
Nondisjunction
Substitution
Trait coded for by an allele on a sex chromosome
The X and Y chromosomes
Diagram that shows the order of genes on a
chromosome
D. Pairs of genes that are inherited together
All chromosomes except the X and Y
Type of mutation where one nucleotide replaces
another
G. Chromosome piece breaks off, flips and reattaches
Chromosomes fail to separate from their matching
partner
I. A piece of one chromosome breaks off and attaches to another
1% frequency of cross-over in a chromosome
Loss of a piece of chromosome due to breakage

3. Somatic-cell mutation Lethal mutation Point mutation
Germ-cell mutation
Somatic-cell mutation
Lethal mutation
Point mutation
Frameshift mutation
Insertion mutation
L. Genetic mutation that causes death
M. Genetic mutation in a body cell
N. Genetic mutation in a gamete cell
O. Mutation in which nucleotides are added
to a gene
P. Any mutation that affects the order and
grouping of all nucleotide bases that
occur after the mutation
Q. Any mutation that occurs in a single gene

4. Answer Key Sex chromosomes B Autosomes E Sex-linked trait A
Linked gene D
Chromosome map C
Map unit J
Deletion K
Inversion G
Translocation I
Nondisjunction H
Substitution F
Germ-cell mutation N
Somatic-cell mutation M
Lethal mutation L
Point shift mutation Q
Frameshift mutation P
Insertion mutation O

5. http://www. internetphotos
Chromosomes
To understand human genetics, we must first understand chromosomes.
Chromosomes are structures made of DNA and proteins that carry heredity information and direct the activities of cells.
Humans have 23 matching pairs of chromosomes (46 total)

6. Sex Chromosomes and Autosomes
Thomas Hunt Morgan discovered that one pair of chromosomes determines the sex of an animal while studying fruit flies.
Called the X and Y chromosomes, or sex chromosomes.
XX = female
XY = male
Charts that show and individual’s full set of
chromosomes are called karyotypes

7. The other chromosomes are known as autosomes.
The sex chromosomes separate along with the other 22 pairs of chromosomes when sperm and egg cells form during meiosis.
Therefore, each egg cell contains an X chromosome.
Sperm cells can contain an X or a Y.
So, it is the father that determines the sex of the child.

8. The Y chromosome contains a gene called SRY (Sex-determining Region Y)
The Y chromosome contains a gene called SRY (Sex-determining Region Y). It produces a protein that causes the development of testes. Without this protein, reproductive organs will develop into ovaries.

9. What’s Going On???
During Morgan’s experiments he discovered something odd. Examine the diagram and try to figure out what’s going on???
Crossing a red eyed fly with a white eyed fly produces all red eyed flies.
What does this tell us about the genes for red and white eyes??
If white is recessive, then we should get ¼ white eyes in the second generation—and we do!!
But…..they are all males!!!! Why???
Answer: Sex-Linked Traits

10. Sex-Linked Traits
Sex-linked traits are traits that are carried on a sex chromosome
Morgan called sex-linked traits:
X-linked (carried on the X chromosome)
Y-linked (carried on the Y chromosome)
Most are carried on the X chromosome and are therefore more common in males.
This is because the matching information on the Y chromosome is missing.
Examples: Color-blindness and Hemophilia

11. Punnett Squares and Sex-linked traits
Normal woman marries a color blind man
XX x XcY
X X Xc Y
XcX
XcX XY XY
There is no chance any of their children will be colorblind.
However, any girl they have will be a carrier.
(Carrier = carries genetic information without showing the trait)

12. What’s Going On???
GgLl X GgLl
Result: 3 Gray, long wings : 1 black, short wings
RrYy X RrYy
Result: 9:3:3: round/yellow
3 round/ green
3 wrinkled/yellow
1 wrinkled/green
Once again, Morgan discovered something odd while studying his fruit flies.
He found two dominant genes (gray body and long wings) did not assort independently as predicted in Mendel’s pea plant experiments.
What’s going on???
Answer: Linked Genes
These genes are carried on the same chromosome

13. Chromosome Mapping
Chromosome map —diagram that shows the linear order of genes on a chromosome.
Developed by using the results of breeding experiments and by looking for the percentage of crossing-over for two traits.
The higher the percentage of crossing-over, the farther away two genes are on a chromosome
Map unit —frequency of 1% cross over

14. Mutations
Mutation—a change in the nucleotide-base sequence of a gene or DNA molecule.
Types:
Germ-cell mutation —occur in gametes/do not affect the organism that produced the gametes /can be inherited
Somatic-cell mutation —occur in body cells/do affect the organisms/can not be inherited
Lethal mutations —cause death, usually before birth
Beneficial mutations —improve chance of survival/provide variation in natural selection

15. Chromosome Mutations Mutations that involve an entire chromosome
Mutations that involve an entire chromosome
Types:
Deletion—loss of a piece of chromosome due to breakage
Translocation—part of a chromosome breaks off and attaches to another chromosome
Inversion—part of a chromosome breaks off, flips, and reattaches
Nondisjuction—a chromosome fails to separate from its partner during meiosis

16. Gene Mutations Point mutation —change that occurs within a single gene
DNA mRNA Amino acid
Point mutation —change that occurs within a single gene
Types: Substitution, Deletion, or Insertion
Substitution—one nucleotide replaces another/result in the production of a different amino acid
Deletions and Insertions do not always result in point mutations. More commonly, they result in Frameshift Mutatons. C T G A
Glutamic
acid
C A T G U A
Valine

17. DNA mRNA Amino acid
Frameshift mutation —results after a deletion has occurred. All remaining codons are incorrectly grouped affecting all remaining amino acids. This can seriously damage the protein.
Can also occur after an insertion of one or more extra nucleotides occurs. A C G T U G C A
Cysteine
Deleted
Glutamic acid
Glutamine
DNA mRNA Amino acid A C T G U G A C
Tryptophan
Serine
Arginine

18. Section 2 Vocabulary Pretest
Pedigree
Carrier
Genetic disorder
Polygenic
Complex character
Multiple allele
Codominance
Incomplete dominance
Sex-influenced trait
Amniocentesis
Chronic villi sampling
Genetic counseling
Gene therapy
Characters influenced by both genes
and environment
Characteristics influenced by many genes
More than two alleles exist for a trait
Way of detecting genetic disorders by
extracting amniotic fluid
Intermediate traits (blending of two)
testing special cells derived from the zygote
Both alleles for a trait are expressed
Disabling conditions with a genetic basis
Diagram that shows inherited traits through
several generations
Have a recessive allele for a trait but do not
show the trait
Informing a person of their genetic makeup
Healthy genes replace defective genes
Male pattern baldness

19. Answer Key Pedigree I Carrier J Genetic disorder H Polygenic B
Complex character A
Multiple allele C
Codominance G
Incomplete dominance E
Sex-influenced trait N
Amniocentesis D
Chronic villi sampling F
Genetic counseling K
Gene therapy L

20. Human Genetics
Pedigree —diagram that shows how a trait is inherited over generations.
Can be used to trace the occurrence of diseases as well.
=male w/ trait
=female w/ trait
= carrier

22. Sex-linked

23. Polygenic Inheritance —many genes control a single trait
Polygenic Inheritance —many genes control a single trait. Examples: hair, eye and skin color, height, and fingerprint patterns

24. Ex: skin color—both genetic and exposure to sun
Complex characters —characters that are influenced strongly both by the environment and by genes
Ex: skin color—both genetic and exposure to sun
Height and weight—both genetic and diet or disease
Some cancers

25. IA and IB are codominant (both expressed in the phenotype)
Multiple alleles —more that two alleles exist for a trait in the population. You still inherit only two—one from mom and one from dad.
Ex: Blood type (Three alleles: IA, IB and i; produce four blood types: A, B, AB, and O)
IA and IB are codominant (both expressed in the phenotype)
i is recessive

26. Try to figure out the missing blood types
Try to figure out the missing blood types. How many can you determine for sure?

27. Sex-influenced traits —males and females have the same genotype but different phenotypes
Ex: Male pattern baldness: The allele is dominant in men but recessive in women due to different levels of testosterone

29. Detecting Genetic Disease
Genetic screening —examination of a person’s genetic makeup. Includes: karyotypes, blood tests for proteins or DNA tests
Genetic screening can be done even before birth:
Amniocentesis —test of amniotic fluid
Chorionic villi sampling —test of cells, derived from the zygote, that grow between the uterus and the placenta
Over 200 genetic disorders can be detected in a fetus using these techniques
Amniotic fluid sample
Chorionic villi sampling

30. Genetic Counseling —medical guidance sought to determine the likelihood of passing on a genetic disorder to a child. Treating genetic diseases is difficult. Usually, we can only treat symptoms.
Gene Therapy is currently being studied as a way to cure genetic diseases like Cystic Fibrosis. It has only been somewhat successful in animal studies.
Remove DNA core from a virus
Inject good genetic material into the virus
Allow virus to deliver the healthy DNA to cells