unit 6

Question 1

what is a gene?

Answer 1

small section of a chromosomes that codes for one protein.

Question 2

how many genes do humans have?

Answer 2

around 30,000

Question 3

what is a allele?

Answer 3

different versions of a gene

Question 4

how many alleles does an offspring receive from each parent for each trait?

Answer 4

one allele from each parent for each trait

Question 5

what are some examples of alleles:

Answer 5

eye color: brown, green, blue, etc.
number of fingers: 5 fingers, 6 fingers

Question 6

who is the father of genetics?

Answer 6

gregor mendel (pea plants)

Question 7

what is a genotype?

Answer 7

the genetic code, the genes or alleles that make up an individual

Question 8

what is phenotype?

Answer 8

the physical appearance of the trait

Question 9

what is a dominant allele?

Answer 9

the allele that is always expressed (appears); only need one copy to show trait, it “wins” - capitol letters are used to show them

Question 10

what is a recessive allele?

Answer 10

needs 2 copies of allele to show the trait (hidden by the dominant allele), it “losses” - use lower case letters to represent

Question 11

what does homozygous mean?

Answer 11

homo = same
purebred
2 alleles for a trait are the same (FF - homozygous dominant, tt - homozygous recessive)

Question 12

what does heterozygous mean?

Answer 12

hetero = different
hybrid
2 alleles for a trait are different (Rr, Tt)

Question 13

what is a dihybrid cross?

Answer 13

a diagram that studies 2 traits on different chromosomes at the same time (RT, rt, Rt, rT)

Question 14

what ratio comes out of two heterozygous traits

Answer 14

9:3:3:1

Question 15

what is another way to do a dihybrid cross?

Answer 15

make two punnett squares and then calculate the probability of event 1&2 by multiplying the probability of event 1 and probability of event 2.

Question 16

what is the definition of simple genetics?

Answer 16

2 traits are present, one dominant and the other one recessive

Question 17

what is the definition of multiple alleles?

Answer 17

more than just 2 alleles are available for a specific trait (ex. hair color)

Question 18

what is incomplete dominance?

Answer 18

heterozygotes show a blending of traits (3 phenotypes)

RR = red
WW = white
RW = pink

Question 18

in humans, there are ___ possible alleles for blood type

Answer 18

3

Question 19

what is co-dominance?

Answer 19

BOTH alleles are expressed (no blending), in the heterozygote

WW = white feathers
BB = black feathers
BW = black AND white feathers

Question 20

what are polygenic traits?

Answer 20

traits controlled by 2 or more genes
poly = many
examples: skin color, height in humans, eye color in humans, cob length

Question 21

how can the environment influence how genes are expressed?

Answer 21

external forces in the environment such as temperature, nutrition, light, etc. can affect how genes are expressed and can therefore affect the organisms phenotype

Question 22

what does it mean to be a carrier?

Answer 22

a heterozygotes individual. they “carry” a recessive allele but do not express that trait

Question 23

which sex has homologous sex crhomosomes?

Answer 23

females (XX)

Question 24

what is the ratio chance of having a boy or having a girl

Answer 24

50-50

Question 25

more males than femeales have recessive sex-linked diseases. why?

Answer 25

males only have one x chromosomes

Question 26

which sex could be a carrier for a trait found on the X chromosome

Answer 26

females

Question 27

what are some examples of sex-linked traits

Answer 27

red-green colorblindness
hemophilia
high blood pressure