Genes

Question 1

What makes you who you are?

Answer 1

We all have characteristics and traits based on what we inherited by our parents in our genes. In addition, environment plats a role in our genes as well.

Question 2

Modifications to Mendelian Genetics

Answer 2

1. Genetic linkage
2. sex-linked genes
3. chromosomal alterations
4. non-traditional patterns of inheritance

Question 3

Genes

Answer 3

• sequences of nucleotides in DNA

- arranged linearly in chromosomes

Question 4

Do all genes assort independently?

Answer 4

• Not true for all genes because some genes are inherited together
• this is because they are linked genes (on the same chromosome)

Question 5

Linked genes

Answer 5

Genes carried on the same chromosome

• linked during transmission from parent to offspring
• inherited like single genes

Question 6

Is there a way t separate two alleles on the same chromosome?

Answer 6

Yes. Through recombination (Prophase 1 in meiosis)

Question 7

Drosophilia melanogaster

Answer 7

A fruit fly

• model organism for animal genetics
• Morgan-first genetic map
• used to test linkage and recombination
• easy, cheap, fast reproduction time, easy to change DNA

Question 8

Key to crossing over

Answer 8

The closer two genes are the more linked they are because there is less change of crossing over between them

Question 9

Normal alleles

Answer 9

• usually the most common allele
• designated by the “+” symbol
• usually dominant

Question 10

Dihybrid Testcross Ratio

Answer 10

1:1:1:1

Question 11

Recombination Frequency

Answer 11

=# of recombinants/ total progeny

Question 12

Double cross over

Answer 12

gene moves during crossover but comes back in a second crossover

Question 13

Can genes on the same chromosome ever assort independently?

Answer 13

Widely separated linked genes often recombine, which makes them appear to assort independently.
50% recombination frequency=independent assortment `

Question 14

Why is there a 50% max

Answer 14

recombination only between 2 of the 4 chromatids so only half of the gametes will have the recombined chromosomes

Question 15

Autosomes

Answer 15

all chromosomes EXCEPT the sex chromosomes

Question 16

Human X chromosome

Answer 16

large (2350 genes)

many x-linked genes are nonsexual traits

Question 17

Human Y chromosome

Answer 17

small (few genes)
very little homology with the X chromosome
contains SRY gene

Question 18

Sex linkage

Answer 18

female need 2 copies of X-linked alleles (homo recessive)

males need 1 copy of X-linked allele

Question 19

X-linked recessive traits more common in males

Answer 19

red-green color blindness, homophilia

Question 20

Pedigree chart

Answer 20

shows the genotype and phenotype in a family’s past generations
square=male, circle=female,blue=wild type, red=homozygous

Question 21

Dosage compensation

Answer 21

in female mammals, inactivation of one X chromosome makes the dosage of X-linked genes the same as males
occurs during embryonic development

Question 22

Barr Body

Answer 22

random inactivation of either X chromosome by condensation

• attached to side of nucleus
• copied during mitosis but always remains inactive

Question 23

Deletion

Answer 23

broken segment lost from chromosome

Question 24

Duplication

Answer 24

broken segment inserted into homologous chromosome

Question 25

Translocation

Answer 25

broken segment attached to nonhomologous chromosome

Question 26

Inversion

Answer 26

broken segment re-attached in reversed orientation

Question 27

CML

Answer 27

cancer of white blood cells

Question 28

ABL gene

Answer 28

• next to the BCR gene it becomes overactive
• codes for tyrosine kinase
• cells grow out of control

Question 29

Gleevac

Answer 29

drug that inhibits tyrosine kinase

Question 30

Nondisjunction

Answer 30

failure of homologous pair separation during meiosis I

increases with womans age

Question 31

Misdivision

Answer 31

failure of chromatid separation during meiosis II

Question 32

Euploids

Answer 32

normal number of chromosomes

Question 33

Aneuploids

Answer 33

extra or missing chromosomes

usually prevent embryo development (except downs)

Question 34

Polyploids

Answer 34

extra sets of chromosomes because the spindle fails during cell division
common and helpful in plants

Question 35

Modes of inheritance

Answer 35

1. Autosomal recessive inheritance
2. autosomal dominant inheritance
3. X-linked recessive inheritance
4. Nontraditional patterns of inheritance

Question 36

Autosomal recessive inheritance

Answer 36

males or females carry a recessive allele on an autosome, homo rec. shows trait
-eg cystic fibrosis, albinism, sickle cell

Question 37

Autosomal dominant inheritance

Answer 37

dominant gene is carried on an autosome
homozygote dominant or hetero show traits
e.g. achondroplaia

Question 38

X linked recessive inheritance

Answer 38

recessive allele carried on X chromosome

e.g. color blindness and hemophilia

Question 39

Prenatal diagnosis

Answer 39

cells obtained from:

• embryo
• amniotic fluid (amniocentensis)
• placenta (chorionic villus sampling)

Question 40

Postnatal genetic screening

Answer 40

biochemical and molecular tests

Question 41

Nontraditional patterns of inheritance

Answer 41

cytoplasmic inheritance and genomic imprinting

Question 42

Cytoplasmic inheritance

Answer 42

• genes carried on DNA in mitochondria or chloroplasts

- follows maternal line

Question 43

Genomic imprinting

Answer 43

expression of an allele is determined by the parent that contributed it

• other is silenced (imprinted allele)
• usually by methylation

Question 44

Igf2

Answer 44

codes for insulin-like growth factor

-paternal copy is active, maternal is imprinted