Medical Genetics- Intro

Question 1

Berg and Boyer’s contributions to genetics

Answer 1

Developed tools that allows scientists to manipulate DNA to more deeply understand their functions and to mass product drugs generated through recombinant technology (i.e.: insulin)

Question 2

Chromosomes

Answer 2

A tightly wound pieces of DNA, house genes

Question 3

Karyotyping

Answer 3

An individual’s chromosomes profile can be analyzed using this technique

This process stains metaphase chromosomes with a Geimsa dye that will stain heterochromatin in distinct, AT-rich banding patterns, sometimes referred to as G-bands

The stained chromosomes are then visualized, organized according to size and matched with its chromosome homolog

Question 4

Nondisjunction

Answer 4

Segregation errors in meiosis

Can lead to germ cells carrying too many or two few copies of affected chromosomes

Question 5

What happens if Nondisjunction occurs during meiosis one?

Answer 5

End up with two cells with no chromosomes

And two cells with each cell having two sister chromatids (2 chromosomes in each cell)

Question 6

What if Nondisjunction happens at the end of meiosis 1?

Answer 6

One cell with nothing
One cell with two sister chromatids (same ones)
Two cells normal with one sister chromatids each

Question 7

Turner syndrome

Answer 7

If a germ cell missing a copy of an X chromosome were to fuse with another germ cell carrying it normal X chromosomal content, the result would be a human with a single X chromosome.

Question 8

Where can mutations occur?

Answer 8

Coding region, promoter region, intron-exon junction

Question 9

Recessive allele

Answer 9

When the mutation eliminates or reduces normal activity of the gene, also known as a loss-of-function mutation

Will only result in a specific phenotype or observed trait when the second copy of the gene is also a recessive allele or when no second copy exists

Question 10

Dominant allele

Answer 10

Increased activity of the gene leading to a gain in [toxic] function

Question 11

linked genes

Answer 11

If two genes are very close to each other on the chromosome, they can be inherited together and can only be separated during recombination in meiosos

Question 12

incomplete dominance

Answer 12

each genotype will show a different phenotype because of differences in gene dosage (ie: flower example)

Question 13

Codominant alleles

Answer 13

each allele can contribute to the phenotype regardless of the presence of absence of any other alleles

ie: blood type

Question 14

Incomplete penetrance

Answer 14

a particular genotype does not manifest itself in the expected phenotype 100% of the time

can be due to either environmental influences or interactions of a particular gene with an individual’s genetic background

Question 15

Modifier Loci

Answer 15

alternate genes in the genome that can affect a particular phenotype associated with a different gene

can influence or prevent phenotypic manifestation of a particular genotype

Question 16

Phenocopies

Answer 16

individuals can expose themselves to an environmental factor that phenotypically mimics a condition present in the family

Question 17

Pleiotropy

Answer 17

When many systems are adversely affected by a single genetic defect (b/c genes have multiple functions in various tissues)

Question 18

Multifactorial inheritance

Answer 18

Joint actions of a large number of genes and outside stimulus in a particular phenotype (can produce a spectrum of observed phenotypes)

Question 19

Acetylation of lysines

Answer 19

Histones have lysines, add acetyl group to the tails to neutralize the positive charge on the lysines –> makes chromatin more open because negative DNA backbone not attracted anymore

associated with open conformation

Question 20

Where does methylation occur on DNA?

Answer 20

cytosine residues of CpG dinucleotides

can be found in promoter regions of the genes and are known at CpG islands

Question 21

What is the methylated state associated with?

Answer 21

Closed conformation and gene silencing

Question 22

Can DNA methylation be propagated?

Answer 22

Yes

1) replication
2) maintenance of methylation

Question 23

Imprinting

Answer 23

genes whose expression is determined by the parent that contributed them

The process begins during gamete formation when

in males certain genes are imprinted in developing sperm and
in females, others are imprinted in the developing egg.

All the cells in a resulting child will have the same set of imprinted genes from both its father and its mother EXCEPT for those cells (“germplasm”) that are destined to go on to make gametes. All imprints — both maternal and paternal — are erased in them.

Question 24

What happens to methylation during gametogenisis?

Answer 24

methylation marks on promoters are erased –> resets the epigenetic status in germ cells