Biology Ch. 2

Question 1

Homologous Chromosomes

Answer 1

Pair of chromosomes (one maternal and one paternal) that contain the same genes in the same locations.

Question 2

Hemizygous

Answer 2

Having one copy of a gene instead of two (male sex chromosomes are XY).

Question 3

Mendel’s Laws

Answer 3

Segregation: gametes only carry one allele for each gene.
Independent Assortment: homologous pairs separate independently from one another.
Dominance: dominant alleles mask recessive.

Question 4

Incomplete Dominance

Answer 4

More than one dominant allele, neither is completely dominant.
Heterozygote will be a blend, red + white= pink

Question 5

Codominance

Answer 5

Both inherited dominant alleles are completely expressed.
Red + white = red and white speckled.

Question 6

Epistasis

Answer 6

One gene’s expression affects the phenotypic expression of another.
If you have a gene for baldness, the gene for hair color is not shown/expressed.

Question 7

Pleiotropy vs. Polygenic Inheritance

Answer 7

Pleiotropy: single gene affects multiple phenotypic traits.
PI: multiple genes affect one phenotype. Usually a spectrum of outcomes; skin tone, height.

Question 8

Penetrance

Answer 8

Probability an organism with a genotype will express the associated phenotype.
Complete would be 100%.

Question 9

X Inactivation

Answer 9

In females, one X chromosome will be methylated and inactivated, called a Barr Body.
Example: calico fu in cats.

Question 10

Chromosome Translocations

Answer 10

2 chromosomes swap segments; can cause size differences.
Called substitution if it is a one-way donation.

Question 11

Helicase
Topoisomerase
Single Stranded Binding Proteins

Answer 11

H: separates DNA strands
T: relieves tension on DNA by unwinding by breaking and rejoining strands.
SSBPs: bind to ss DNA near rep fork to keep strands apart.

Question 12

Primase
DNAP III
DNAP I
Ligase

Answer 12

P: creates RNA primer needed for rep initiation.
DNAPIII: synthesizes DNA in 5’ to 3’ direction.
DNAP I: removes RNA primer after replication and replaces with DNA.
L: seals gaps in phosphodiester bonds.

Question 13

Transcription Initiation, Elongation, and Termination

Answer 13

I: RNAP binds to promoter (TATA) with help of TC factors.
E: RNA is synthesized 5’-3’ using antisense strand as template.
T: RNAP meets AAA rich region and detaches.

Question 14

RNA Splicing and Alternative Splicing

Answer 14

RNA: removing introns and connecting remaining exons.
AS: combining exons in different ways to code for multiple proteins.

Question 15

Translation Initiation, Elongation, Terminatioin

Answer 15

I: small subunit binds to mRNA, methionine tRNA attaches to start codon, large subunit binds.
E: tRNAs carrying AAs enter A site, pp chain from P site attaches to tRNA in the A site, then it shifts to P site while the old tRNA exits through E site.
T: stop codon enters A site and release factors cause everything to disassemble and release peptide chain.

Question 16

Silent, Missense, and Nonsense Mutations

Answer 16

S: codon is changed but AA is unchanged.
M: substitution causes AA change.
N: substitution changes to a stop codon.

Question 17

Genome
Transcriptome
Proteome

Answer 17

G: complete genetic information of an organism.
T: set of all RNA molecules that a cell can produce.
P: complete set of proteins in an organism that are expressed.

Question 18

Gene Density

Answer 18

Percentage of genome consisting of coding genes.
Prokaryotes genes are more dense than eukaryotes because they don’t have introns.
The vast majority of the human genome is noncoding.

Question 19

Temperature-Dependent Sex Determination:
Pattern I and Pattern II

Answer 19

Pattern I: males develop in cold, females develop in warm (turtles).
Pattern II: females develop in hot/cold, males develop in medium (crocodiles).

Question 20

DNA Methylation and Histone Acetylation

Answer 20

Methylation: stops gene expression by condensing into heterochromatin.
Acetylation: increases expression by loosening into euchromatin.

Question 21

RNA World Hypothesis

Answer 21

Self replicating RNA molecules were precursors to life.
RNA can store genetic info like DNA and can catalyze chemical reactions like enzymes.

Question 22

Light Microscope
Scanning Electron Microscope
Transmission Electron Microscope
Fluorescence Microscope

Answer 22

LM: visible light to view thin sample; need to stain; kills cells.
SEM: used to view Surface of 3D objects with high res; kills sample.
TEM: thin cross sections of internal structures at high magnification; kills sample.
FM: fluorescent probes that bind to specific things; can be used on live cells.

Question 23

Order of pellet formation in Centrifugation

Answer 23

Largest/most dense form pellet first.
Nucleus > mitochondria/chloroplasts > ribosomes.

Question 24

Microarray

Answer 24

Used to monitor expression of large groups of genes across a genome.

Question 25

Southern Blot
Northern Blot
Western Blot

Answer 25

S: DNA
N: RNA
W: Protein

Question 26

Pasteur’s Experiment

Answer 26

Disproved spontaneous generation.
Curved neck flask experiment.

Question 27

Griffith’s Experiment

Answer 27

Proved transformation.
Made a non-virulent bacteria virulent by exposing it to virulent bacteria DNA.

Question 28

Avery-MacLeod-McCarty

Answer 28

Found DNAse prevented transformation.
Used similar methods to Griffith.

Question 29

Hershey and Chase

Answer 29

Showed phages used DNA for genetic material.
Used radioactively labeled P (DNA) and S (proteins).

Question 30

Meselson and Stahl

Answer 30

Proved semiconservative replication.
Used 2 isotopes of N in nucleotides and found that daughter strand contained one of each.

Question 31

Gurdon

Answer 31

Proved fully differentiated cells have full genome.
He removed a nucleus from a frog’s intestinal cell and was able to make a full individual out of that DNA.