Hereditary

Question 1

p21

Answer 1

• Tumor suppressor gene
• inhibits cyclin dependent kinase (CDK) activity —> decreases the frequency of cell division (CDK stimulates cell division; p21 inhibits phosphorylation activity in order to decrease excessive cell division)
• Haplosufficient
• Important gene in regulating cancer by regulating cell division

Question 2

Which chromosome are the majority of sex-linked disorders passed down through?

Answer 2

Due to the size difference, the majority of sex-linked disorders are passed down through X-chromosome linkage

Question 3

Down syndrome

Answer 3

trisomy at chromosome 21
a result of nondisjunction at chromosome 21, producing a zygote with 2n+1 (47) chromosomes
it is a trisomy that is non-fatal —> the altered chromosomes does not kill the embryo

Question 4

Haplotype

Answer 4

A group of genes that are located so close to each other on a chromosome that they tend to be inherited together
Because the genes are clustered together, they tend to not be split via crossing over (recombination event) and are often found in offspring

Question 5

p53

Answer 5

A tumor suppressor gene
Plays numerous roles in cancer prevention
upregulated (increase in its protein production) in response to cell stress

Question 6

One loss-of-function mutation in p53 would result in what?

Answer 6

No effect
Loss-of-function in both copies of the genes are required for cancer causing, null tumor suppressor alleles

Question 7

Pleiotropy

Answer 7

When one gene affect many different traits

Ex: cystic fibrosis
A single gene will lead to the expression of cystic fibrosis, a disease that cause the expression of different symptoms in different tissues

Question 8

Epistasis

Answer 8

An interaction between genes where one gene affects the expression of different genes

Ex: hair varieties

Question 9

Heterozygous organisms

Answer 9

Organisms that posses a dominant allele on one of their homologous chromosomes (homolog) and a recessive allele (for the same gene) on the other homolog

Question 10

Heterozygous organism

Answer 10

Organisms that posses a dominant allele on one of their homologous chromosomes (homologs) and a recessive allele (for the same gene) on the other homolog

Question 11

During crossing over, what structures do homologous chromosomes form when they physically join together?

Answer 11

Form a tetrad (or bivalent)
Occurs doing prophase of meiosis I

Question 12

Allele

Answer 12

Variance of a gene that has different forms
Found on the same loci on both chromosomes in a homologous pair
Ex: various color alleles at the eye color gene locus, such as brown eyes or blue eyes

Question 13

Oncogenes

Answer 13

Genes that can transform a normal cell into a cancerous cell

Question 14

Test cross

Answer 14

Used t determine an unknown parental genotype, based on the phenotypes seen in the offspring generations
One parents of an unknown genotype will be bred with a parent that is phenotypically recessive with genotype homozygous recessive

Question 15

Turner syndrome

Answer 15

• X chromosome monosomy that only affects females
• A female will have one X chromosome (deletion of one X chromosome), leading to 2n-1 (45) chromosomes
• Usually does not cause any intellectual disability’s but it does lead to physical abnormalities and sterility- short stature, gonadal dysgenesis, heart defects, kidney abnormalities
• XO genotype

Question 16

Proto-oncogenes

Answer 16

Genes involved with control and regulation of cell division and can become oncogenes (cancer-causing genes) due to gain-of-function mutation
Follow the one-hit-hypothesis

Question 17

One-hit-hypothesis

Answer 17

A gain-of-function mutation in one copy of the gene is enough to produce a mutant phenotype (turns into an oncogene)

Proto-oncogene + gain-of-function mutation = oncogene

Question 18

Gain-of-function mutations

Answer 18

Can cause too much protein to be made which results in over expression of a gene or production of an over-active protein which results in an increase in gene product activity, cancerous growth occurs as a result

Question 19

Two-hit hypothesis

Answer 19

Loss-of-function mutations in both copies of the gene are needed to produce a mutant phenotype (cancer causing)

Question 20

Haploinsufficiency

Answer 20

When one copy of the gene is lost or nonfunctional and the expression of the remaining copy is not sufficient enough to result in a normal phenotype- it can result in an intermediate phenotype
The normal trait requires two functional gene copies to produce enough protein to show the trait

Question 21

Haplosufficiency

Answer 21

One copy of the gene is sufficient enough to achieve a normal phenotype because it produces enough protein to show the trait
The normal trains only requires one functional copy

Question 22

During DNA methylation, where are the methyl groups added to the genome?

Answer 22

to the nitrogenous bases on a DNA strand

Question 23

what is the function of DNA methylation?

Answer 23

inhibiting gene expression by two mechanisms:
1) blocking transcription from occurring by preventing transcription proteins from binding to the DNA strand
2) DNA that has been methylated can wrap tightly around histones through the recruitment of specific proteins, preventing access to methylated DNA

Question 24

what is DNA demethylation?

Answer 24

the removal of the methyl group on the nitrogenous base which results in increased gene expression (gene upregulation)

opposite of DNA methylation which upregulats

Question 25

what is histone acetylation?

Answer 25

the addition of an acetyl group to the amino acid *lysine* found in the *histone tails* that protrude from one histone core

Question 26

what is the result of histone acetylation?

Answer 26

causes DNA to wrap less tightly around histones, leading to an *increase* in gene expression --> weakens the electrostatic affinity/interaction between DNA and histone proteins due to histones becoming less positive *associated with euchromatin

Question 27

what epigenetic regulation is present in the inactive X chromosome of females compared to the active X chromosome?

Answer 27

DNA methylation: the inactive X chromosome is heavily methylated compared to the active DNA regions --> this is known as the *barr body* (located on the periphery of the ell nucleus)

Question 28

prader-willi syndrom

Answer 28

* occurs due to **genomic imprinting** * a set of genes on chromosome 15 inherited from the mother are inactivated, while the same genes on the copy of chromosome 15 inherited from the father are left active * occurs when the genes on the paternal copy of the chromosome are deleted or mutated and the child does not have active gene expression from either chromosome

Question 29

what is genomic imprinting?

Answer 29

* the alteration in expression of a gene is dependent on which parent the gene was inherited from * only one allele of the gene is expressed --> the genes on a chromosome from one parent are imprinted (silenced via DNA methylation) while genes on the chromosome from the other parent are expressed (activated via histone acetylation)

Question 30

histones

Answer 30

* positively charged, basic proteins * organize and condense DNA * bond between (+) histones and (-) DNA is an *ionic bond*

Question 31

transcriptome

Answer 31

* the entire set of mRNA expressed by a cell

Question 32

proteome

Answer 32

* entire set of proteins expressed by a cell

Question 33

sanger sequencing

Answer 33

* amplification of DNA and use of fluorescence to determine the order of the genetic sequence

Question 34

cri du chat

Answer 34

caused by deletion on chromosome 5

Question 35

klinefelter's syndrom

Answer 35

* caused form an extra X chromosome leading to an XXY genotype

Question 36

how can a fetus be tested for genetic disorders?

Answer 36

* amniocentesis or * chorionic villus sampling (CSV)

Question 37

what are 3 sex-linked recessive conditions?

Answer 37

* hemophilia * color blindness * Duchenne's muscular systrophy

Question 38

hemophilia

Answer 38

* sex-linked recessive condition * causes abnormal blood clotting

Question 39

color blindness

Answer 39

* sex-linked recessive disorder * primarily observed in males

Question 40

duchenne's muscular dystophy

Answer 40

* sex-linked recessive disorder * progressive loss of muscle

Question 41

phenylketonuria (PKU)

Answer 41

* autosomal recessive disorder * inability to produce the proper enzymes for phenylalanine breakdown * causes degradation product, phenylpyruvic acid to accumulate

Question 42

cystic fibrosis

Answer 42

* autosomal recessive disorder * causes fluid builduo in respiratory tract

Question 43

tay-sachs

Answer 43

* autosomal recessive disorder * lysosome defect in which cells can't breakdown lipids for normal brain function

Question 44

huntington's disease

Answer 44

* autosomal dominant disorder * nervous system degeneration

Question 45

achondroplasia

Answer 45

* autosomal dominant disorder * causes dwarfism

Question 46

hypercholesterolemia

Answer 46

* autosomal dominant disorder * excess cholesterol in blood that progresses into theart disease

Question 47

viroids

Answer 47

* smaller than viruses * circular RNA molecules that infect plants * they do not encode for proteins, they replicate in host plant cells via host enzymes * cause errors in the regulatory system of plant growth

Question 48

prions

Answer 48

* not virus or cell * infectious, mis-folded versions of proteins in the brain * cause normal versions of proteins to become mis-folded * fatal * implicated in diseases like mad cow, kuru, scrapie the sheep and creutzfeldt-jakob disease

Question 49

retrovirus

Answer 49

* single-stranded RNA virus * uses **reverse transcriptase** to make complement DNA from their RNA by hijacking the host cells replicating machinery * the RNA is then used to manufacture mRNA or enter the lysogenic cycle (encorperated into host cell) * ex: HIV