Transmission Genetics

Question 1

What are Mendel’s 4 postulates?

Answer 1

1. Unit factors are in pairs
2. Dominance/Recessiveness
3. Random Segregation
4. Independent assortment

Question 2

What is a phenotype?

Answer 2

physical appearance of a characteristic

Question 3

What is a gene?

Answer 3

unit of inheritance (unit factor)

Question 4

What is an allele?

Answer 4

alternative forms of a single gene, located on homologous chromosomes

Question 5

What is a genotype?

Answer 5

genetic makeup of an individual

Question 6

What does a monohybrid cross examine?

Answer 6

one character, one pair of contrasting traits

Question 7

What does a dihybrid cross examine?

Answer 7

two characters, two pairs of contrasting traits

Question 8

What does a trihybrid cross examine?

Answer 8

three characters, three pairs of contrasting traits

Question 9

What is a proband on a pedigree?

Answer 9

individual whose phenotype first brought attention and led to the construction of the pedigree

Question 10

What are the characteristics of autosomal recessive traits?

Answer 10

typically skip generations and appear equally in both sexes

Question 11

What are the characteristics of autosomal dominant traits?

Answer 11

typically appear in each generation and appear equally in both sexes

Question 12

What is a locus?

Answer 12

location of gene on chromosome

Question 13

What is incomplete dominance?

Answer 13

parents with contrasting traits produce offspring with intermediate phenotype (Red Parent + White Parent = Pink Offspring)

Question 14

What is codomindance?

Answer 14

in heterozygote influence of both alleles is evident (show both phenotypes)

Question 15

What are lethal alleles?

Answer 15

Alleles that can kill

Question 16

What are recessive lethal alleles?

Answer 16

• can be tolerated in heterozygotes but lethal in homozygotes
• death depends on need of gene product
• circulates but never eliminated from population

Question 17

What are dominant lethal alleles?

Answer 17

• time of death depends on need of gene product
• easily eliminated from populations if lethal before sexual maturity

Question 18

What is epistasis?

Answer 18

(Stoppage) expression of one gene or gene pair masks or modifies the expression of other genes

Question 19

What are the different types of epistasis?

Answer 19

• homozygous recessive gene at one locus overrides alleles at other loci
• single dominant allele at the first locus influences the expression of alleles at a second locus
• two gene pairs complement each other

Question 20

What is pleiotropy?

Answer 20

(many affecting) one gene can affect multiple traits- the gene product is involved in multiple biochemical pathways and processes

Question 21

What is sex linkage?

Answer 21

gene is located on the sex chromosome

Question 22

What are the different types of sex linkage?

Answer 22

X-linked genes and Y-linked genes

Question 23

What is hemizygous?

Answer 23

neither dominant nor recessive

Question 24

Characteristics of X-linked genes?

Answer 24

• recessive alleles always expressed in males
• many X linked disorders
• lethal X linked disorder affect males, females are carriers

Question 25

What are characteristics of Y-linked genes?

Answer 25

• traits in Y chromosome only found in males
• father’s Y chromosome traits passed to all sons
• dominance irrelevant in Y-linkage because Y is hemizygous

Question 26

What is sex limited inheritance?

Answer 26

expression of specific phenotypes is limited to one sex only, influenced be sex hormones

Question 27

What is sex influenced inheritance?

Answer 27

gene expression in heterozygotes influenced by sex hormones

Question 28

What is genetic suppression?

Answer 28

suppressor genes do not let the expression of mutant phenotype

Question 29

What is position effects?

Answer 29

phenotypic expression of genes depends on the physical location of the gene on chromosome

Question 30

What is penetrance?

Answer 30

the individuals that show at least some degree of expression of a mutant phenotype

Question 31

What is expressivity?

Answer 31

reflects the range of expression of a mutant phenotype

Question 32

What is genetic anticipation?

Answer 32

onset and severity of genetic disorders tend to progress with each successive generation

Question 33

What is genetic regulation?

Answer 33

changes in DNA sequence and genetic code

Question 34

What is epigenetic regulation?

Answer 34

changes in gen regulation

Question 35

What are paternally imprinted genes?

Answer 35

paternal allele epigenetically modified and inactivated

Question 36

What are maternally imprinted genes?

Answer 36

maternal allele epigenetically modified and inactivated

Question 37

What is heteroplasmy?

Answer 37

one cell contains many chloroplasts and mitochondrial genomes

Question 38

What type of inheritance are chloroplasts and mitochondria?

Answer 38

maternally inherited

Question 39

What are the characteristics of mitochondrial disorders?

Answer 39

• maternally inherited
• disorder must reflect deficiency in bioenergetic function in the organelle
• affects most energy demanding organs- brain/muscles
• specific genetic mutation in one or more mitochondrial genes

Question 40

What is an example of a human mitochondrial disorder?

Answer 40

MERRF- Myoclonic Epilepsy and Ragged-Red Fiber disease

Question 41

What are the characteristics of cloning by nuclear transfer?

Answer 41

• clone’s nuclear genome from desired animal
• clone’s mitochondrial genome from egg donors
• mitochondrial genomes different from the sire

Question 42

What is the maternal effect?

Answer 42

offspring’s phenotype for a particular trait is controlled by gene products present in the egg before fertilization

Question 43

What are the products of nuclear genes of female gamete and what is their role?

Answer 43

proteins, mRNAs, and microRNAs: after fertilization these play essential role in regulating early embryonic development