week 1: human genetics, genetic disorders

Question 1

what is a genome?

Answer 1

The genome is all the DNA in the cell.

All the DNA on all the chromosomes.

Question 2

what are the three genomes a eukaryotic cell can have?

Answer 2

1. nuclear genome
2. Mitochondrial genome
3. plastid genome

Question 3

What is genomics?

Answer 3

it is the study of genomes including large chromosomal segments containing many genes.

Question 4

how many chromosomes does a human somatic cell contain?

Answer 4

22 autosomal pairs and one sex chromosome (total of 23)

Question 5

how does alternative splicing effect polypeptide production?

Answer 5

human genomes can produce more than one polypeptide per gene because of alternative splicing of RNA transcripts.

Question 6

what method was used during the human genome project?

Answer 6

The genome was completed using sequencing machines and the dideoxy chain termination method

Question 7

what is the structure of the human genome?

Answer 7

contains regulatory sequences, exons and introns

Question 8

what contributes to non coding DNA

Answer 8

1. introns
2. regulatory elements of genes
3. multiple copies of genes, including pseudogenes
4. intergenic sequences
5. interspersed repeats

Question 9

what are pseudogenes?

Answer 9

former genes that have mutated and are no longer functional

Question 10

what are transposable elements?

Answer 10

move from one site to another in a cell’s DNA

Question 11

eukaryotic transposable elements have two types; what are transposons and retrotransposons?

Answer 11

transposons move by means of a DNA intermediate and require a transposase enzyme.

Retrotransposons move by means of an RNA intermediate using a reverse transcriptase.

Question 12

what are Alu elements?

Answer 12

they are transcribed into RNA molecules; some are thought to help regulate gene expression.

Question 13

what is a series of repeating units of 2 to 5 nucleotides called?

Answer 13

Short Tandem Repeat (STR)

Question 14

________ are variations in the number of repeats of specific DNA sequences

Answer 14

STR’s

Question 15

how will a mutation affect a genome?

Answer 15

a single base may mutate or a large segment of a chromosome

Question 16

what type of mutation is passed onto offspring somatic (body) cell or germ-line mutations.

Answer 16

germline mutation are passes on and somatic mutations are not passed on and usually give rise to cancer or other diseases.

Question 17

what is a mutagen?

Answer 17

a natural or human made agent (physical or chemical) which can alter the structure or sequence of DNA.

Question 18

name 4 types of chemical mutagens

Answer 18

1. base analogs (bromouracil)
2. chemicals which alter structure and pairing of bases (nitrous acid)
3. intercalating agents (ethidium bromide)
4. DNA structure altering (peroxides)

Question 19

name 2 types of radiation mutagens

Answer 19

EM spectrum and ionizing radiation

Question 20

what is a point/substitution mutation?

Answer 20

a base change in the DNA.
can be silent missense or nonsense.

Question 21

describe insertion or deletion mutations

Answer 21

addition or removal of one or more nucleotides.
introduces a frameshift mutation.

Question 22

describe an allele (3 things)

Answer 22

-an allele is a variant from a gene
-humans are diploid organisms as they have two alleles at each genetic locus
-one allele is inherited from each parent.

Question 23

difference between dominant and recessive alleles

Answer 23

a recessive allele only shows if there are two present

a dominant allele always shows

Question 24

what types of gene disorders can be inherited?

Answer 24

autosomal recessive and sex linked

Question 25

how is sickle cell anemia cause and what are the symptoms?

Answer 25

caused my a missense mutation

-red blood cell is an abnormal crescent shape.
-hemoglobin is abnormally shaped.
-forms clumps and does not move easily through blood vessels.

Question 26

cystic fibrosis:

is it a recessive or dominant disorder?

what are the symptoms?

Answer 26

autosomal recessive disorder

-thick mucus in lungs
-constant lung infections and impaired digestion

it affects 1 in 2500 white births

Question 27

what causes cystic fibrosis?

Answer 27

deletion mutation which causes there to be an amino acid missing in the protein and it cant fold correctly.

Question 28

is PKU recessive or dominant?

Answer 28

it is an autosomal recessive disorder.

Question 29

what causes PKU?

and what are the symptoms?

how is it regulated?

Answer 29

it is the deficiency of an enzyme that is required for the proper metabolism of amino acid phenylalanine.

loss of the PAH enzyme results in mental retardation, organ damage, unusual posture and ca compromise pregnancy

regulated through strict diet with no dairy (low in phenylalanine and high in tyrosine

Question 30

describe Huntington’s disease/chorea

(3 points)

Answer 30

it is an autosomal DOMINANT disorder

it is an inherited degenerative brain disorder eventually resulting in loss of mental and physical control

chorea means “dance like movements” and refers to the uncontrollable movements.

Question 31

what are the 4 types of chromosomal mutations?

Answer 31

translocation
inversion
duplication
deletion

Question 32

describe translocation chromosome mutation

Answer 32

segments of different chromosomes are exchanged

an example is Burkitt’s Lymphoma
(cancer of the lymph nodes, in children)

Question 33

describe inversion chromosome mutation

Answer 33

a segment of the chromosome is flipped
(inverted)

an example is Four-Ring Syndrome
(cleft pallate, club feet, testes don’t descend)

Question 34

describe duplication chromosomal mutation

Answer 34

a segment of one chromosome moves to the same location of a homologous chromosome

an example is Charcot–Marie–Tooth disease
(high arched foot, claw feet, confined to a
wheelchair)

Question 35

describe a deletion chromosomal mutation

Answer 35

a segment of a chromosome is removed

one example is cri du chat - deletion of part of chromosome 5.

Question 36

what is nondisjunction?

Answer 36

chromatids fail to separate during meiosis.

Question 37

what is an aneuploidy

Answer 37

a gamete that contains an abnormal number of chromosomes.

Question 38

examples of diseases that occur with nondisjunction

Answer 38

1. down syndrome - caused by having one extra 21st chromosome
2. Kleifelter’s syndrome - occurs when a male has one extra x chromosome.
3. occurs when females have one less x chromosome.