Chapter 7 - The Inheritance of Single-Gene Differences Flashcards
Reasons why man is an unsuitable research subject
- has long life cycle
- can’t be made to interbreed randomly. Can only bear a comparatively small no. of progeny
- can’t be subjected to rigorous experimental conditions
methods used to study human genetics
- Pedigree analysis
- Karyotyping
- mode of transmission can be revealed
- also known as family histories
pedigree analysis
- stained preparations of mitotic metaphase chromosomes are potographed, individual chromosomes are cut apart and arranged in pairs
- one can detect numerical and structural abnormalities
karyotyping
chief method used in human genetics
pedigree analysis
what can be observed in families
inheritance of traits
a pedigree indicates the structure of a family __
schematically
pedigree give information on:
- dominance or recessiveness of alleles
- risks (probabilities) of having affected offspring
Modes of Transmission of Hereditary Traits
- autosomal dominance
- autosomal recessive
- sex-linked dominance
- sex-linked recessive
trait that is due to an __ __ gene never skips a generation
autosomal dominant
- marriage between affected individuals produces offsprings who are also affected by the trait
- affected progenies may also result from mating between unaffected parents if they are heterozygous for the gene pair
autosomal recessive
pedigrees show affected males with unaffected wives transmit the trait to daughters only
sex-linked dominance
pedigrees show affected families with unaffected husbands transmit the traits to sons only, although the daughters are carriers of the gene
sex-linked recessive
Example of autosomal dominant disorder
achondroplasia
Examples of autosomal recessive disorders
- phenylketonuria
- cystic fibrosis
- sickle cell
- hereditary disorder characterized by lung congestion and infection and malabsorption of nutrients by the pancreas
- most common disease in the US
- affected individuals die before reproductive age
cystic fibrosis
why is there a high frequency of cystic fibrosis carriers
due to overcompensation
- average no. of children in families with CF child is 25% higher than normal families
encodes a large protein that functions in cell membrane to regulate water balance inside cells
CF gene
what does defective CF protein prevent
chlorides ions from exiting cells, resulting in excess water inside the cell
act as recessive traits in females, but dominant traits in males
x-linked recessive disorders
Examples of x-linked recessive disorders
- hemophilia A
- fragile X syndrome
- Duchenne muscular dystrophy
- colorblindess
hereditary hemorrhagic disorder resulting from a congenital deficit of factor VIII that manifests as protracted and excessive bleeding either spontaneously or secondary to trauma
hemophilia A
inherited genetic disorder that causes physical abnormalities, behavioral issues and a wide range of other health problems, including: Developmental delays. Intellectual disabilities. Learning disabilities. Anxiety.
Fragile X syndrome (FXS)
- most common hereditary neuromuscular disease and does not exhibit a predilection for any race or ethnic group
- Mutations in the dystrophin gene lead to progressive muscle fiber degeneration and weakness.
Duchenne muscular dystrophy
classification of chromosomes according to centromeric position
- metacentric
- submetacentric
- acrocentric
- telocentric
centromeres in the middle of the chromosome
metacentric
centromeres slightly off center
submetacentric
centromeres almost at the ends
acrocentric
terminal centromeres
telocentric
Examples of Inherited Human Traits
- widow’s peak
- straight hairline
- hitchhiker’s thumb
- tongue rolling
- bent little finger
- cleft chin
- hand clasping
- unattached/attached ear lobes
