Inheritence

What is an autosome?

any chromosome that is not a sex chromosome

What does diploid mean?

having 2 alleles at most loci (location on chromosome)

What does dominant mean in relation to gene inheritence?

The dominant allele results in the phenotype when present even if the second allele is not the same allele (heterozygous)

What does genetic variation mean?

differences in DNA sequence between individuals

What does genome mean?

whole set of haploid chromosomes

What is genotype?

complete set of genetic material, specifically taking into account differences from other individuals

What is the definition of germline?

cells that form gametes

What is haploinsufficiency?

when a single normal allele is not sufficient to produce the normal phenotype

What does heterozygous mean?

Both the dominant and recessive alleles are present, dominant phenotype though

What does homozygous mean?

Both alleles are the same, can be dominant or recessive

What is lineage?

descent from common ancestor

What does matrilineal mean?

descent through the female line

What is the definition of mitochondria?

organelle whose more important function is to produce ATP for the cell

What is a modifier gene?

a gene that can alter the expression of a separate gene

What is monogenic?

controlled by 1 gene

What does patrilineal mean?

descent through the male line

What is a pedigree?

maps lineage

What does polygenic mean?

multiple genes

What does recessive mean in relation to genetic inheritence?

allele that only results in its phenotype when homozygous, is overpowered by dominant allele when heterozygous

What is recombination?

homologous chromosomes swap some sequences

What is an SNP?

single nucleotide polymorphism, single base-pair change in an allele

What does somatic mean?

body, somatic cells are body cells

What does x-linked inactivation mean?

one random x in females is transcriptionally active, irreversible

What’s the definition of traits/phenotype?

observable characteristics

What is simple inheritence?

mendelian inheritance, phenotypic outcome is result of a single gene

What is a complex trait?

A trait that is influenced by multiple genes and environmental factors

What are characteristics of the nuclear genome?

is made up of autosomes and sex chromosomes, 3.4 B bases, ~20k genes, inherited form both parents, lots of recombination, lots of variable regions

What are characteristics of the mitochondrial genome?

circular and double-stranded, 16k bases, 35 genes, maternally inherited, no recombination occurs, good for studying lineage

What are some examples of relevant simple inheritance patterns?

breeding for dairy production, blood types, calico cats and x-linked inactivation, USDA scrapie eradication program

What are some examples of complex inheritance patterns?

body size, morphology, and lifespan

What 2 main factors control simple inheritance pedigree patterns?

chromosomal location of the gene

phenotype expression pattern for the allele of interest

What are the typical modes of simple inheritance?

1- autosomal dominant

2- autosomal recessive

3- x-linked dominant

4- x-linked recessive

Where do all blood type alleles come from?

single glycosyltransferase gene (ABO gene)

How does the O antigen result?

a single bp deletion that leaves only H-antigen no extra group

What is the difference between A and B blood types?

7 SNP changes between them, results in substrate specificity change (A= galactose B= acetylglucosamine)

How do many recessive genetic disorders arise?

recessive alleles cause enzyme defects, can be corrected sometimes with gene therapies that replace 1 allele and prevent clinical problems

How can dominant disorder result?

1- haploinsufficiency

2- domoinant negative effect

3- gain of function

What is the dominant negative effect?

altered gene product antagonizes the normal product

What is gain of function?

changing the gene product’s specificity or expression pattern rather than reducing or eliminating it

What are characteristics of autosomal dominant inheritance?

disease not obscured in pedigress (every affected animal has an affected parent)

one copy of the mutation is sufficient to cause disease so occurs in heter and homozygotes

male to male transmission of disease is possible

Homozygotes amy be rare because disease is often more severe than heterzygotes

What are the characteristics of autosomal recessive inheritance?

disease alleles are obscured in pedigrees (affected animals may not have affected parents)

2 copies of mutation needed to cause disease (homo- recessive)

affected animals inherit one mutant allele from each parent

parents may inherit allele from same source due to inbreeding

What are the characteristics of x-linked inheritance and x inactivation?

males are hemizygous for x-linked traits (AY or aY)

males show the trait whether or not allele they have is dominant or recessive (since they only have 1)

females have 2 x chromosomes just like autosomes can be homo or heterozygous

in female somatic cells x-inactivation means only 1 x is transcriptionally active, cells from the same cell will have same inactive x, females are mosaics of x-linked gene expression

heterozygous female may have disease as a result of skewed distributionof cells with active x bearing the disease (calico cat)

What are the characteristics of x-linked dominant inheritance?

disease no obscured in pedigrees (every affected animal has affected parent)

male to male transmission not possible

all female offspring of affected male are affected

pattern of inheritance through females is the same as autosomal dominant inheritance

x-linked dom. traits more frequently observed in females, heterozygous females are usually more mildly affected than hemizygous males

What are the characteristics of x-linked recessvie inheritance?

trait is seen more frequently in males than females

male to male transmission not possible

female offspring of affected amles are obligate carriers

affected females are homozygous, results from mating between affected sire and carrier dam