Exam 1

Question 1

What are the 3 classic divisions of genetics?

What does each deal with it?

Answer 1

• Transmission genetics: inheritance
• Molecular genetics: biochemical genetics
• Population genetics: evolution and adaption

Question 2

List the contributions to medical genetics of each model organism

• Drosophila melanogaster
• Escherichia coli
• Caenorhabditis elegans
• Arabidopsis thaliana
• Mus musculus
• Saccharomyces cerevisiae (yeast)

Answer 2

• Drosophila melanogaster: sex linked traits
• Escherichia coli: genetic code
• Caenorhabditis elegans: Apoptosis
• Arabidopsis thaliana: Plant genomics
• Mus musculus: cancer
• Saccharomyces cerevisiae (yeast): control mechanisms of the cell cycle and mitochondrial genetics

Question 3

What are the 4 major types of genetic disorders?

Answer 3

• Chromosome disorders
• Multifactorial disorders (more prevalent)
• Single-gene disoders
• Mitochondrial disorders

Question 4

____ and ____ are are pyrimidines where as ____ and _____ are purines

Answer 4

• Cytosine/Thymine
• Adenine/Guanine

Question 5

How many hydrogen bonds does A and T/U have? G and C?

Answer 5

2, 3

Question 6

Chromosomes contains…?

Answer 6

Genes

Question 7

Somatic cells contain ____ pairs of chromosomes, for a total of ____. One pair is the sex chromosomes while the other ____ pairs are called _____.

Answer 7

23, 46, 22, autosomes

Question 8

Autosomes are ____ of each other

Answer 8

Homologs

Question 9

Somatic cells work in pairs. This makes them ____ whereas gametes are _____ and have ____ total chromosomes

Answer 9

Diploid, Haploid, 23

Question 10

T/F: Bacteria lack histones

Answer 10

True

Question 11

What does DNA Polymerase do?

Answer 11

Synthesizes DNA by assembling nucleotides and proofreads them to ensure that the added nucleotide is complementary

Question 12

Where does transcription take place? Translation?

Answer 12

Nucleus, Cytoplasm

Question 13

What are transcription and translation both mediated by?

Answer 13

RNA

Question 14

____ initiates mRNA transcription by binding to the promoter region

Answer 14

RNA Polymerase II

Question 15

The template strand is the ____ strand and is ____ to the RNA transcript.

The nontemplate strand is the ____ strand and is ____ to the RNA transcript.

Answer 15

• Antisense, Complementary/Anti-parallel
• Sense, Identical/Parallel

Question 16

What is the purpose of the 5’ guanosine cap?

Answer 16

Helps the RNA molecule from being degraded and marks the starting position for translation

Question 17

What is the purpose of the 3’ poly-A tail?

Answer 17

Adenine bases are added to the 3’ end of the RNA molecule to prevent the mRNA from degrading when it reaches the cytoplasm

Question 18

_____ contains most genes, is loosely organized, and transcription is more active. In comparision, _____ contains less genes, is more compact, and transcription is less active

Answer 18

Euchromatin, Heterochromatin

Question 19

In eukaryotes, what happens before the mature transcript is formed?

Answer 19

Exons are spliced out of primary mRNA

Question 20

What are the 3 stop codons?

Answer 20

UAA, UGA, UAG

Question 21

What 3 letter code signifies the start codon? What AA does this specify?

Answer 21

AUG, Methionine

Question 22

Name the 3 phases of Interphase

What occurs during this process?

Answer 22

• G1 –> S –> G2
• DNA replication and protein synthesis

Question 23

Chromosomes reach their most highly condensed state and arrange at the middle of the spindle during what phase?

Answer 23

Methaphase

Question 24

Crossing over in meiosis ocurs during what phase?

Answer 24

Prophase 1

Question 25

During what phase does the nuclear envelope disappear?

Answer 25

Prophase

Question 26

What is the major difference between Interphase 1 and Interphase 2?

Answer 26

No DNA replication ocurrs during Interphase 2

Question 27

How many mature sperm are produced during spermatogenesis?

Answer 27

4

Question 28

Describe oogenesis

Answer 28

Question 29

# Define: - Alleles - Locus - Genotype

Answer 29

* Alleles: Different versions of the same gene (ex. eye color) * Locus: Location of a gene * Genotype: The combination of alleles that is present at a given locus (ex. HH, Hh, hh)

Question 30

T/F: A person with different alleles on a gene is said to be a homozygote

Answer 30

False: heterozygote

Question 31

What are the 3 types of point/single base pair substitutions?

Answer 31

1. Silent mutation 2. Missense mutation 3. Nonsense mutation

Question 32

Base pair substitution that does not change the genetic code

Answer 32

Silent mutation

Question 33

Base pair substitution that alters one amino acid

Answer 33

Missense mutation

Question 34

Base pair substitution that produces a stop codon in the mRNA

Answer 34

Nonsense mutation

Question 35

What are the 3 types of DNA segments (multiple base pairs) mutations?

Answer 35

1. Deletions or Insertions 2. Duplications of whole genes 3. Mobile DNA elements - Transposons

Question 36

A Frameshift mutation consists of \_\_\_\_\_. It is especially harpmful because it shifts the \_\_\_\_\_.

Answer 36

Deletions/Insertions, Reading frame

Question 37

Explain the mechanism behind cystic fibrosis

Answer 37

* Changes one AA (CFTR) by deleting 3 bps * Most common deletion is a 3-bp deletions that deletes phenylalanine (missense mutation) * Chloride ion channels are effected which creates a salt/water imbalance and effects breathing

Question 38

Charcot-Marie-Tooth Disease is an example of a \_\_\_\_. This ocurrs on chromosome 17. This gene is said to display \_\_\_\_.

Answer 38

Duplication, Gene dosage/Dosage sensitivity

Question 39

* Involved in some cases of Duchenne muscular dystrophy, B-thalassemia, and familal breast cancer * Can self-replicate without DNA polymerase

Answer 39

Transposons

Question 40

Describe promoter mutations

Answer 40

Decreases the affinity of RNA polymerase for a promoter site --\> Decrases production of mRNA --\> Decreases protein production

Question 41

Splice-site mutations can occur at ____ or ____ sites within mRNA introns. If these mutations occur *_on_* these sites it results in _____ which can be partial or complete. However, if these mutations occur *_near_* these sites it results in _____ which can also be partial or complete.

Answer 41

* Acceptor/Donor * Intron inclusion * Exon exlusion

Question 42

The donor site occurs at what sequence and at what end of the splice site? Acceptor site?

Answer 42

* Donor: GT sequence, 5' * Acceptor: AG sequence, 3'

Question 43

Tandem repeats usually repeat the 3-bp sequence \_\_\_\_. A normal amount or repeats is ____ but when _____ of repeats occur, this can cause genetic disease. This usually occurs during ____ and is passed on from \_\_\_\_\_

Answer 43

* CAG * 10-30 * Hundreds to thousands * Meiosis * Mother to son

Question 44

What are the 4 classifications of mutations?

Answer 44

1. Substitution/Single base pair mutation 2. DNA segements (multiple base pairs) 3. Within regulatory sequences 4. Tandem repeat sequences-expanded repeats

Question 45

3 molecular consequences of mutations (protein-coding genes)

Answer 45

1. Gain of function 2. Loss of function 3. Dominant negative mutation

Question 46

Describe Gain of function, Loss of function, and Dominant negative mutations

Answer 46

* Gain of function: * Dominant * Over expression/Inappropriate expression of (gene dosage) * Rately produces novel protein function

Question 47

Describe Loss of function

Answer 47

* Loss of function: * Recessive * 1 allele mutated --\> 50% loss of protein --\> Heterozygote ok * **Haploinsufficiency**: The 1 copy is not enough which results in dominance --\> 1 allele mutated --\> disease state * Ex. Familial Hypercholesterolemia

Question 48

Describe Dominant negative mutations

Answer 48

* Dominant negative mutations * Abnormal protein will manifest as dominant and inhibit the function of the normal protein product * Commonly seen in multi-protein complexes

Question 49

Describe induced mutations

Answer 49

* Attributed to environmental causes * Can casue base substitutions, deletions, and frameshifts * Mutagens: * _Radiation_: Ionizing = dsDNA breaks, Nonionizing = pyrimidine dimers and kinks * _Base analogs_