Genetics Exam 1

What is a genotype?

the sum of genes

What is the most common chromosome?

X chromosome

What was the first cloned gene sequence?

beta-globin

What is a karyotype?

the number and visual appearance of the __chromosomes__ in the cell __nuclei__ of an __organism__ or species.

What is a phenotype?

everything that is not the DNA or genotype

What does it mean to be macroscopic?

you do not need anything to view it

What does it mean to be microscopic?

you need a microscope to view it

What decides how you look?

protein

What makes up genetic material?

proteins

What makes up proteins?

amino acids

What is a nuclear location?

part of the chromosome is in the nucleus

What type of strands do viruses have?

double and single stranded DNA and RNA

How did the mouse die from the S cells when there was only dead S cells being put in the body?

the S cells told the R cells to become S cells and ended up killing the mouse

What does DNA stand for?

dexyribo-nucleic-acid

What does RNA stand for?

ribo-nucleic-acid

What base pairs are in DNA?

adenine, guanine, cytosine and thymine

What base pairs are in RNA?

adenine, guanine, cytosine and uracil

What are polymers of nucleotides?

polynucleotides

What makes up a nucleotide?

sugar, phosphate, nitrogenous base

What nucleic acid is this?

purine

What nucleic acid is this?

adenine

What nucleic acid is this?

guanine

What nucleic acid is this?

pyrimidine

What nucleic acid is this?

cytosine

What nucleic acid is this?

Uracil

What nucleic acid is this?

thymine

What are the building blocks of DNA?

nucleotides

Is DNA or RNA more stable?

DNA

What does a nucleoside contain?

a sugar and base

What does a nucleotide contain?

sugar, base and a phosphate group

What end is the 5’ end?

phosphate

What end is the 3’ end?

hydroxyl group

How many nucleotides are in a polynucleotide?

30+

What is Chargaff’s rule?

A=T and G=C

Who found that DNA is a double helix and when?

Watson and Crick

Why can hydrogen bonds form?

because of the polarity they attract

How many hydrogen bonds do A=T and G=C make?

A=T - 2

G=C -3

What is the diameter of a double helix?

2 nm

What is the distance of 1 turn of the helix and how many base pairs are there?

3\.4 nm with 10 base pairs per turn

What much DNA is in one cell?

2 m

What percentage of a cell does DNA take up?

50%

What are the characteristics of the double helix?

antiparallel strands

complementary bases inside forming H-bonds

sugar-phosphate backbone to the outside

What makes up the energy of the double helix?

1/3 bonding energy- base pairing (hydrogen bonds)

2/3 bonding energy- base stacking (interaction of aromatic ring system)

How many chromosomes are in the human genome? How many nucleotide pairs are there?

46 chromosomes and 6.6 x 10^9 nucleotide pairs

How long are DNA loops?

40,000 base pairs long

What is a primer?

short RNA molecule

What type of model is DNA replication?

semiconservative model

What is the semiconservative model?

one strand becomes the template for the replication

What is the conservative model?

The entire molecule is replicated and not split

What is the dispersive model?

bits and pieces of the molecule are broken up and replicated

What is DNA polymerase?

the product is DNA and the reaction is a polymerase

What does it mean to be primer dependent?

needs a short nucleic acid to start, roughly 10 nucleotides long. The enzyme is primase that makes small RNA molecules

What is helicase?

unwinds DNA

What is primase?

makes RNA primer

What is DNA ligase?

puts DNA fragments together

What is gyrase?

winds the DNA together

What does helicase use to separate the DNA strands?

ATP

What is the replication fork?

where helicase opens up the DNA

What are the 2 DNA strands called?

leading strand and lagging strand

What is another name for the lagging strand?

okazaki fragments

What are the 4 steps of discontinuous replication of the lagging strand?

\-primer synthesis by primase

\-elongation by DNA polymerase III

\-primer removal and gap filling by DNA polymerase I

\-ligation of nicks by DNA ligase

What does exonuclease do?

removes the primer and proof reads the DNA and puts the correct nucleotide in

How long does it take to replicate an E. Coli genome?

84 minutes

What is the advantage of using an RNA primer?

removal of error containing fragments which arise at the beginning of the polymerization

What is the advantage of using an RNA primer? Why 5’ to 3’ synthesis?

after nucleotide removal during proofreading the energy for the next synthesis step comes from the incoming dNTP

What is positive supercoiling?

unwinding of the DNA at the replication form leading to over twisting of the double helix

What is the role of the topoisomerases?

gives the DNA the opportunity to rotate back from its supercoil to relieve stress

How much does the DNA molecule rotate per minute?

2400

What is the central dogma?

DNA→ RNA → protein

What is it called when RNA→DNA?

reverse transcriptase

What does a telomere do?

repeats 5-8 nucleotide pattern to stop the strand from decreasing

What is half a chromosome called?

chromatid

What is an exon?

it codes for a protein

\`How much of a human gene is introns?

95%

What is the longest exon and what is it on?

17106 bp on TTN

How many chromosomes are in a human?

46

What is the composition of chromosomes by mass?

1/3 DNA

1/3 histones

1/3 non-histone proteins

What type of charge does DNA have?

negatively charged

What type of charge does Lysine and arginine have?

positively charged

What does a motor protein do and where is it?

its in the middle of non-histone proteins because of the microtubules from the spindle fibers

What is the order of chromatin compaction and by how much?

nucleosomes (7 fold)

superhelix (40-50 fold)

radial loop-scaffold (10,000 fold)

What are the features of yeast cells?

they do not have histones, they are not that compact

What pattern is the superhelix in?

solenoid and zigzag

How are the chromatin arranged?

in radial loops

What blocks transcription?

histones

What is chromatin remodeling?

they move the nucleosomes

What does acetlyation/lysine do?

it makes the nucleosomes/chromatid structure more loose

What happens when you take away the acetylation?

the nucleosomes become tighter and you may not be able to do transcription

What is a lysine?

a positively charged amino acid

What is a characteristic of an acid?

donates hydrogen

What is a characteristic of actyline?

negatively charged

What does lysine + acetyline =

neutral + DNA = loosens the DNA structure

What things help with the “opening” of chromatin?

\-DNA binding proteins

\-histone modifying enzymes

\-nucleosome remodeling complexes

What happens during the maintenance of histone modification?

the old histones act like a template while putting the new histones in

What is a chromosome in regards to chromatin?

a highly condensed chromatin

What is constitutive?

typically a highly repetitive sequence that is always condensed/compact

What is facultative?

condensation varies with cell type, developmental stage, chromosome

What is heterochromatin?

chromatin that is never released

What is an example of facultative heterochromatin?

inactived x-chromosome in females

What is a mutation?

a heritable change of the DNA sequence of an organism