1. Chapter 14 – The Human Genome Human Chromosome 3 Suzanna Macedo 2010

2. Karyotype – a picture of all the human chromosomes

3. Sex chromosomes – determine gender
males = XY females = XX

4. Autosomes – all other chromosome pairs (44)
Huntington’s Disease is an autosomal-dominant disease.

5. A Family Tree
To understand how traits are passed on from generation to generation, a pedigree, or a diagram that shows the relationships within a family, is used. In a pedigree, a circle represents a female, and a square represents a male. A filled-in circle or square shows that the individual has the trait being studied. The horizontal line that connects a circle and a square represents a marriage. The vertical line(s) and brackets below that line show the child(ren) of that couple.

6. 1. This pedigree shows the inheritance of attached ear lobes
1. This pedigree shows the inheritance of attached ear lobes. Which parent has attached ear lobes?
2. How many children do the parents have? Which child has attached ear lobes?
3. Which child is married? Does this child’s spouse have attached ear lobes? Do any of this child’s children have attached ear lobes?

7. Dominance and Recessiveness in Humans
Blood Groups – 3 alleles for blood type: IA, IB or i
IA and IB are codominant
i is recessive

8. Recessive Alleles
a. some homozygous combinations of
recessive alleles cause genetic diseases
* PKU - phenylketonuria
b. a person with one normal allele and one
recessive is called a carrier

9. Dominant Alleles
a. always expressed (only need one allele)
i. achondroplasia

10. Codominant Alleles
a. both alleles are expressed, can show
as intermediate phenotype
i. sickle cell anemia

11. Sex – Linked Genes – any gene on one or both of the sex chromosomes.
Males have just one X chromosome, so any trait on the X chromosome is expressed (shows up), even if they are recessive.

12. Queen Victoria of England was a carrier of the gene for
                                    
Queen Victoria ( )
Queen Victoria of England was a carrier of the gene for
hemophilia.  She passed the harmful allele for this X-linked
trait on to one of her four sons and at least two of her five
daughters.  Her son Leopold had the disease and died at
age 30, while her daughters were only carriers.  As a result of
marrying into other European royal families, the
princesses Alice and Beatrice spread hemophilia to Russia,
Germany, and Spain.  By the early 20th century, ten of
Victoria's descendents had hemophilia.  All of them were men,
as expected.

13. caused by Autosomol Disorders Recessive alleles Dominant alleles
Codominant alleles
include
include
include
Albinism
Galactosemia
Tay-Sachs disease
Huntington’s disease
Sickle cell disease
Cystic fibrosis
Phenylketonuria
Achondroplasia
Hypercholes-
terolemia

14. Homologous chromosomes fail to separate
Chromosomal Disorder
Nondisjunction – failure of the chromosomes to properly divide into gametes. End result is missing or extra chromosomes.
Homologous chromosomes fail to separate
Meiosis I:
Nondisjunction
Meiosis II

15. Examples: Down Syndrome (Trisomy 21)
or Klinefelter syndrome (XXY) in males

16. Detecting and Treating Genetic Disorders
Sequencing
Start signal
Promoter
Stop signal
Gene

17. DNA Fingerprinting
Restriction enzyme
Restriction enzymes are used to cut the DNA into fragments containing genes and repeats. Note that the repeat fragments from these two samples are of different lengths.
Chromosomes contain large amounts of DNA called repeats that do not code for proteins. This DNA varies from person to person. Here, one sample has 12 repeats between genes A and B, while the second sample has 9 repeats.
The DNA fragments are separated according to size using gel electrophoresis. The fragments containing repeats are then labeled using radioactive probes. This produces a series of bands—the DNA fingerprint.

18. Gene Therapy Nucleus Bone marrow cell Normal hemoglobin gene
Chromosomes
Genetically engineered virus