Genetic Control of Inheritance

Question 1

arrangement of chromosomes by size and shape

Answer 1

karyotype

Question 2

another word for meiosis

Answer 2

gametogenesis

Question 3

alleles

Answer 3

normal variations in genes

Question 4

gene symbol and protein designation nomenclature for mice and rats

Answer 4

gene symbols in italics with first letter capitalized, protein designations all caps and not italicized

Question 5

gene symbol and protein designation nomenclature for humans, etc.

Answer 5

gene symbols in italics with all letters capitalized, protein designations all caps not italicized

Question 6

5 components to labeling location of genes on a chromosome

Answer 6

1. chromosome
2. arm
3. region
4. band
5. sub-band

Question 7

which processes occur during meiosis I that allow for problems to potentially arise?

Answer 7

crossing over, which means that homologous chromosomes exchange genetic material
random assortment, where homologous chromosomes randomly segregate into daughter cells

Question 8

transition

Answer 8

one purine for another purine

Question 9

transversion

Answer 9

a purine for a pyrimidine or vice versa

Question 10

polygenic trait

Answer 10

traits that are determined by multiple genes located on more than one chromosome

Question 11

multifactorial events

Answer 11

represent the additive effects of abnormal genes and environmental factors

Question 12

do congenital disorders (inherited disorders that manifest at birth) that involve endocrine disruption usually have a genetic component?

Answer 12

No, usually these are based more on environment than genetics

Question 13

mutations of single genes in somatic cells

Answer 13

can cause dysfunction, but are not transmitted to offspring (because somatic cells do not undergo meiosis)

Question 14

mutations of single genes in sperm or ova

Answer 14

are transmitted to subsequent generations via meiosis following the specific inheritance pattern for that gene

Question 15

two main inheritance patterns

Answer 15

mendelian inheritance: autosomal dominant or recessive traits
sex-linked traits: X-linked dominant affect both males and females, X-linked recessive affect males and homozygous recessive females

Question 16

autosomal dominant diseases usually affect

Answer 16

structural proteins and receptors (remember this is mendelian inheritance)

Question 17

autosomal recessive disorders usually involve

Answer 17

an enzyme defect (remember this is mendelian inheritance, as opposed to sex-linked inheritance pattern)

Question 18

sex-linked recessive traits are most commonly seen in

Answer 18

males (heterozygous, XY) who lack the matching normal gene on the Y chromosome that would control the defective gene on their only X

Question 19

what is a barr body

Answer 19

the inactive x chromosome in a cell

Question 20

explain mosaicism of the x chromosome

Answer 20

in females, an x chromosome (either from mom or dad) is randomly inactivated in each cell early in development. from that initial inactivation, the same one will continue to be inactivated in all the daughter cells in that cell line. as a result, females have some regions of cells with an x from dad and some regions with an x from mom. males are not mosaics regarding x-linked genes because they only have one x chromosome.

Question 21

explain escape genes

Answer 21

some genes on x chromosome escape inactivation and are still functional. most of these genes are also present on the y chromosome

Question 22

pathophysiologic implications of escape genes

Answer 22

klinefelter’s syndrome: XXY, results in overdose of escape genes due to extra x’s
turner’s syndrome: XO, results in lack of escape genes because no second x to from which to get escape genes, and also don’t get them from a y

Question 23

chromosomal abnormalities usually result from an error in

Answer 23

meiosis (specifically meiosis I) during crossover and random distribution

Question 24

translocation

Answer 24

abnormal placement of part of a chromosome

Question 25

deletion

Answer 25

altered structure of chromosome

Question 26

duplication

Answer 26

abnormal number of chromosomes

Question 27

what is a common cause of spontaneous abortions during the first trimester

Answer 27

displacement or loss of DNA fragments, resulting in a form of Down syndrome

Question 28

non-disjunction

Answer 28

a numerical mutation in which chromosomes do not separate equally during meiosis, results in 22 or 24 chromosomes in the egg or sperm

Question 29

mosaicism

Answer 29

non-disjunction of chromosomes during MITOTIC division in early embryonic period, resulting in two chromosomally different cell lines from a single fertilized egg. this most commonly happens with sex chromosomes (example, turner’s syndrome)

Question 30

translocation

Answer 30

structural abnormality involving an interchange of genetic material between non-homologous chromosomes (different from non-disjunction, which is incorrect separation of chromosomes during cell division). translocated fragment is functional!!

Question 31

non-disjunction occurs where

Answer 31

can happen in meiosis or mitosis, but most commonly happens in meiosis I

Question 32

describe the philadelphia chromosome

Answer 32

a reciprocal translocation in which the telomeric portion of 22q switches with the telomeric portion of 9q (basically, two parts of chromosomes just swap places) - this specific translocation creates a hybrid bcr-abl gene, which has strong tyrosine kinase activity and encourages uncontrolled cell proliferation (CML)

Question 33

describe the two types of non-reciprocal (unbalanced) robertsonian translocation

Answer 33

1. the mother is a carrier, meaning she has 45 chromosomes and one copy of chromosome 21 has been translocated onto chromosome 14. mother passes down a chromosome 14 and a chromosome 21, which also has a chromosome 14 stuck to it. father passes one chromosome 14 and one 21. child has 46 chromosomes, but has three copies of chromosome 21
2. child has 47 chromosomes and an extra chromosome 21, has to do with non-disjunction?

Question 34

how do mitochondria arise?

Answer 34

from pre-existing mitochondria

Question 35

what does mitochondrial DNA encode?

Answer 35

some subunits of enzymes, rRNA’s, and tRNA’s needed for mitochondrial protein synthesis, which will be synthesized entirely in the mitochondria
remember: most mitochondrial proteins are encoded by nuclear DNA, which will be made in the cytosol and imported into the mitochondria!!

Question 36

what are most proteins encoded by mDNA used for?

Answer 36

oxidative phosphorylation!

Question 37

define replicative segregation

Answer 37

replicated mitochondria segregate randomly into daughter cells
- homoplasmy: daughter gets only normal or only mutant mitochondria
- heteroplasmy: daughter gets mixture of normal/mutant mitochondria

Question 38

describe maternal mitochondrial inheritance

Answer 38

mitochondria are located in the midpiece of the sperm, and only the cell body goes into the egg. also, any paternal mitochondria that do get into the egg are eliminated via the ubiquitin-proteasome system