quiz 1: genetics

Question 1

Genetics influences disease risk in multiple ways.

Answer 1

First, the presence of certain variations of a gene can predispose someone to a disease or be directly causative of that disease. Second, heritable and non-heritable traits that turn certain genes “on” and “off”, influencing their expression can predispose someone to a disease or be directly causative of that disease. Finally, gene-gene interactions or gene-environment interactions can predispose someone to a disease or be directly causative.

Question 2

Some background you may have forgotten:

Answer 2

DNA consists of four chemical nucleotides or bases: adenine (A), cytosine (C), guanine (G) and thymine (T). DNA is stored (in humans) as double-stranded chromosomes, meaning that there are two strings of bases that match up with each other. An A pairs with a T and a C pairs with a G. The sequence of these bases serves as an instruction manual to the cell to generate RNA, a single-stranded string of nucleotides, except where thymine is replaced with uracil (U). RNA can serve functions on its own, or it can code for proteins. (We used to think all the important DNA coded for proteins and the rest was “junk” DNA, but now we know differently.) For some more review and a little more detail on DNA structure, see this (optional)

Question 3

germ cells

Answer 3

(egg and sperm)

Question 4

We call these changes single nucleotide polymorphisms, or SNPs.

Answer 4

there are random mutations that happen over time in germ cells (egg and sperm) that are passed through generations. Typically, these mutations change just one base pair, so instead of having an “A-T” pair at position 235,692 on chromosome 14, now it’s a “C-G” pair.
we study the frequency of SNPs in a population to determine if they cause disease

Question 5

genetic epidemiology

Answer 5

a relatively new discipline that seeks to elucidate the role of genetic factors and their interaction with environmental factors in the occurrence of disease in populations

Question 6

major allele vs minor allele

Answer 6

in a SNP the one that occurs for most people is referred to as the major allele, whereas the one that occurs less frequently is the minor allele

Question 7

expressed,

Answer 7

meaning it is transcribed into RNA and/or protein
Genetic variation only “shows” if it is expressed

Question 8

epigenetics

Answer 8

There are changes that happen inside the nucleus of the cell that make some genes express more than others. Some of these changes are heritable, meaning the fact that a gene or copy of a gene is turned off is passed through generations in germ cells. Other changes are not heritable. We refer to the changes that determine gene expression

Question 9

Nucleosomes:

Answer 9

146 base pairs of double helical DNA wrapped around eight histones

Question 10

Histone:

Answer 10

proteins that act as a center for DNA to wrap around in its condensed form

Question 11

Histone acetyltransferase (HAT):

Answer 11

enzyme that starts acetylation (adds acetyl groups)
Causes the uncoiling of DNA which allows the genes to be accessed for transcription and the expression of genes

Question 12

Histone deacetylase (HDAC):

Answer 12

enzyme that removes acetyl groups to balance acetylation, causes DNA to maintain condensed form causing less expression of genes (

Question 13

Euchromatin:

Answer 13

Loosely packed transcriptionally active DNA

Question 14

Heterochromatin:

Answer 14

Densely packed transcriptionally inactive DNA

Question 15

Methylation:

Answer 15

gene silencing, permanent method of downregulation transcription of genes

Question 16

Gene Silencing:

Answer 16

stably alter the expression of genes happens when stem cells turn into cells for different tissues. Prohibits binding of transcription proteins to the gene physically and keeps DNA compact so it can not be transcribed.

Question 17

common complex diseases

Answer 17

A common complex disease is one for which symptoms may arise due to a variety of underlying factors. An example of this is asthma.

Question 18

epistasis

Answer 18

gene-gene interaction is epistasis. In cases of epistasis, There are lots of ways that genes interact with each other. One example is if a small change in gene A creates changes in the protein produced by gene A, which then determines whether the DNA for gene B gets transcribed into RNA.

Question 19

ethical issues

Answer 19

list

Question 20

Why haven’t we found the gene for that? What is the gene for that?

Answer 20

For common complex diseases (usually chronic): diseases that are common, but have many different contributors/influences (Ex: ASTHMAS:air quality, physical activity, elevation, genes, maternal smoking, early respiratory infections, and many more)
Genetic treatments becoming an option (genetic therapy)
Screening moving along a lot faster less risk, and secondary prevention

Question 21

DNA to protein trasnformation:

Answer 21

ACTG nucleotides in DNA tell us when it starts, stops, and the code for genes in between.
gene=protein
DNA to mrna transcription: unzip DNA and proteins come in and make the mrna copy then translation: mrna goes through ribosome to create protein groups of 3 nucleotides create the start codon stop anticodon and each of the amino acids in between that come together to form protein

Nucleus has the copy of the DNA and it has to stay safe in there. We need to get the instructions to make proteins out to the ribosome outside of the nucleus. mRNA is the photocopy carried to the ribosome but it is single strand and ACUG instead of ACTG

Question 22

Why can’t we tell which gene is causing the problem:

Answer 22

it can be multiple mutations or genes, genes can interact with one another, different mutations can cause the same common complex disease. Also certain genes turn others on and off or interact.

Question 23

Public health application:

Answer 23

secondary prevention: screening
Symptoms
Genetic mutations screening on the population level
Dilemmas: Will there be action taken if people learn they are at risk, discrimination, increased risk doesn’t mean they are 100% guaranteed to get the disease, hesitancy to know if you are at risk or not, sometimes you can be at risk and still do nothing to prevent/treat it
Currently: breast cancer, infant/newborn screening

Question 24

Tiers:

Answer 24

Tier 1: clinical should be used in clinics, lots of evidence (multiple sclerosis gene)
Tier 2: not as much evidence, nice to know because you may be able to help prevent/treat (alzheimer’s gene)
Tier 3: not very much or no evidence, messy, should not be used clinically (23 and me)

Question 25

table 3

Answer 25

see screenshot