exam 2.1 genetics

Question 1

What is a karyotype and what is an ideogram (remember that mutations have to be larger than 4mb to be seen on a karyotype)

Answer 1

karyotype- the particular chromosome set of a species

ideogram- physical drawing representation

Question 2

What are the parts of a chromosome

Answer 2

long arm- p
short arm- q
centromere
sister chromatids
non-sister chromatids

Question 3

How may pairs of autosomes, and how many sex chromosomes do humans have?

Answer 3

autosomes- 22 pairs

sex- 2

Question 4

How does the medical and general usage of the word “gene” differ?

Answer 4

medical- only parts that code for proteins are genes

general- any functional unit

Question 5

What is a locus?

Answer 5

the exact location of a gene on a chromosome

Question 6

What are alleles?

Answer 6

genes that have two or more variations in a population (eye color)

Question 7

What is the difference between genotype and phenotype?

Answer 7

genotype- genetic combination of alleles that a person has for a specific trait
phenotype- how that trait is physically expressed

Question 8

What is a SNP?

Answer 8

single nucleotide polymorphism- when one single nucleotide is replaced by another (normally only have two alleles)

Question 9

List the ways autosomal dominant and autosomal recessive modes of inheritance differ?

Answer 9

autosomal dominant- need only one gene. doesn´t skip generations, equally affects male and female

autosomal recessive- need both genes, skips generations, equally affects males and females

Question 10

Which parent do you inherit your mitochondrial DNA from?

Answer 10

mother

Question 11

What are the genetic principles of pleiotropy, aneuploidy, and anticipation

Answer 11

plietropy- single gene mutation affets several organ systems(Marphan´s)
aneuploidy-one extra or one less chromosome
anticipation- current generation develops disease sooner than those in earlier generations (Huntington’s)

Question 12

For X-linked recessive inheritance, who is affected and who is a carrier (i.e. male vs female)?

Answer 12

affected- males
carriers- females
*it is possible for a female to get the disease, but her mother must have been a carrier and the father affected

Question 13

Why are females more likely to get an X-linked dominant disease than males?

Answer 13

females only need to inherit one mutant gene, affects heterozygous females(double the chances of inheriting a mutant X)

Question 14

What are the major features of Turner syndrome, Why is it called a mosaic disease?

Answer 14

X-chromosome monosomy, 45 X, 46 XX, 47XXX

short stature, ovarian dysgenesis, neurocognitive problems

Question 15

Why should we consider many sex chromosomes aneuploidies as traits, not diseases as they have been classified in the past?

Answer 15

Some cause no serious health issues (ie taller than average)

Question 16

Why is fragile x syndrome called “fragile”, and what are some of its major features?

Answer 16

unstable CGG sequence- ends appear to be hanging

most common form of inherited mental retardation

Question 17

What is the difference between imprinting of the X chromosome, and imprinting of the autosomes?

Answer 17

Imprinting ensures that only one of the inherited alleles (the non-imprinted one) is ever expressed in the individual, and it’s dependent on the parent it comes from.
Imprinting on the X chromosome results in total silencing of an entire chromosome.
Imprinting on autosomes results in silencing of individual genes.
Silencing means that the gene is permanently turned off and will not be transcribed.

Question 18

Prader-Wili and Angelman syndrome are examples of this epigenetic disease process___?

Answer 18

Imprinting

Question 19

What are the five points of control for gene expression?

Answer 19

1. Chromatin State
2. Transcriptional State
3. Translational state
4. post translational control into cytoplasm
5. post translational modification

Question 20

What is the most studied control for gene expression in terms of epigenetic influence?

Answer 20

1. Chromatin state

Question 21

Why does DNA naturally wrap around histones?

Answer 21

DNA has a negative charge and histones are positive

Question 22

What epigenetic changes can occur to histone tails to encourage or discourage winding/unwinding?

Answer 22

Histone acetylation- nuetralizes charge and DNA opens up and can be actively transcribed
histone methylation: down regulates trsncription
Modifications: methylation, acetylation, ubiquination, sumoylation, phosphorylation

Question 23

What is a promoter region on a gene?

Answer 23

area where transcription starts

Question 24

Why are promoter regions generally not methylated

Answer 24

you don’t want to silence the gene

Question 25

What is a non-mutagen epigenetic carcinogen?

Answer 25

They mutate the epigenetics, not the actual DNA

Question 26

How do Hat-HDAC drugs work?

Answer 26

Hystone acetyl trasnferase and Hisdtone deacetylase- try to influence cancer genes by influencing chromatin remodeling and gene transcription

Question 27

Are all genes proto-oncogenes?

Answer 27

No. They are involved in speeding up or inhibiting the cell cycle, so when mutated they can cause cancer

Question 28

How do oncogenes and tumor suppressors differ?

How many alleles in each example need to be mutated in order for cancer to form?

Answer 28

Tumor supressors- inhibit the cell cycle. you need two mutated alleles to be affected
oncogenes- stimulate the cell cycle. you need one mutated allele to be affected