lecture 1- genetics review

Question 1

definition of genome

Answer 1

all the genetic info in an organisms chromosomes

Question 2

definition of chromosome

Answer 2

a linear arrangement (eukaryotes) of genes and other DNA

Question 3

a gene is the fundamental unit of ___ that carries __ from __ to __

Answer 3

heredity
information
from one generation to the next

Question 4

describe genome size

Answer 4

come in all sizes

• genome size is not specifically correlated with its number of genes
• chromosome number is also not correlated with size

Question 5

describe chromosome size

Answer 5

lots of variation- physical and gene number

• number of chromosomes per genome (lots of variation)
  humans- 23 chromosomes
  dog- 39
  honey bee- 16

Question 6

central dogma

Answer 6

DNA -replication-> DNA -transcription-> RNA -translation-> protein

• central dogma of info transfer in the cell

Question 7

protein structural levels

Answer 7

primary –> secondary –> tertiary –> quaternary

Question 8

name 7 gene parts

Answer 8

start codon
stop codon
intron
exon
promoter
3’ UTR
5’ UTR

Question 9

what is start codon

Answer 9

the first 3 base pairs of the gene (ATG aka AUG)

Question 10

what is stop codon

Answer 10

last 3 base pairs of the gene that code for stop (TAA, TAG, TGA- aka UAA, UAG, UGA)

Question 11

what is exon

Answer 11

part of the gene transcribed into RNA after splicing

Question 12

what is intron

Answer 12

part of gene that is removed after transcription to RNA

Question 13

what is promoter

Answer 13

region of DNA (not transcribed) where RNA polymerase binds and containing info about where and when to express gene

Question 14

what is 5’ UTR

Answer 14

part of the mRNA from the 5’ end to the first translated codon

Question 15

what is 3’ UTR

Answer 15

part of the mRNA from the 3’ end of the last translated codon

Question 16

protein structure basics- there are many diff types of protein domains and motifs (8)

Answer 16

N terminal
binding domain (DNA, substrate)
transmembrane domains
protein specific motif
modification site- phosphorylation, PO4
protein-protein interaction domain
cellular targeting sequence
C terminal

Question 17

an allele is one of a series of ____ of a given gene at a ____ that differ in ___ and often result in ___

Answer 17

alternative forms
single locus
DNA sequence
altered protein expression

Question 18

a locus is a…

Answer 18

specific place on a chromosome

Question 19

what are the most prominent examples for alleles and dominance

Answer 19

diploid organisms, where one allele is inherited from each parent

Question 20

define genotype

Answer 20

the genetic makeup of the organism as distinguished from its physical appearance

Question 21

define phenotype

Answer 21

the observable properties of an organism produced by its genotype

Question 22

three organisms with the same genotype would have very diff ___ depending on the dominance of the ___

Answer 22

phenotypes
alleles

Question 23

describe how changes in yellow and blue dominance changes phenotype

Answer 23

yellow dominant, blue recessive –> yellow
blue dominant, yellow recessive –> blue
yellow dominant, blue dominant (co-dominance) –> green

Question 24

definition of epigenetics

Answer 24

the study of changes in organisms caused by modifications of gene expression rather than alterations in genetic code

• these changes can and often are heritable

Question 25

epigenetic alterations do NOT occur in the…

Answer 25

DNA nucleotide sequence (A,T,C,G’s)

Question 26

compare between epigenetic and genetic phenomena

Answer 26

mendelian genetics: if phenotype mutant –> genotype mutant

epigenetics: phenotype mutant –> genotype wild-type, or genotype mutant –> phenotype wild-type

Question 27

name 3 common epigenetic mechanisms

Answer 27

1- DNA methylation (a subset of cytosine residues could be modified by methylation)

2- histone modifcation/histone variants
. deacetylated “closed” nucleosome –> transcription off
. acetylated, “open” histone –> transcription on

3- regulatory non-coding RNA’s (ncRNA’s or RNAi)

Question 28

example of gene silencing by methylation/histone modification

Answer 28

during early embryogenesis, there is a random inactivation of one X chromosome in females (XX) in 2 diff cells to prevent overexpression of X chromosomal genes

consequence- one allele is expressed in some parts of the body and the other allele in other parts of the body

ex:
males:
XaY = red
XbY = black
females
XaXa = red
XbXb = black
XaXb = red and black spotted

Question 29

what consequence can methylation have on a gene?

Answer 29

can block transcription/expression of a gene- similar to a mutation
Promoter methylation –> no transcription

Question 30

describe example of how epigenetics can be environmentally triggered and inherited

Answer 30

agouti gene in mouse: when methylated –> agouti gene silenced, healthy mouse with brown fur

• when not methylated –> agouti gene continuously active –> mouse with yellow fur, obesity & diabetes
• twins: genes can be specifically turned off in one twin due to environmental factors- affecting the methylation status
• methylation status can be inherited in the next generation, maintaining epi-allele status