chapter 9: genes and inheritance

Question 1

heredity

Answer 1

gene that is passed from parent to offspring

Question 2

single-gene trait

Answer 2

traits determined by instructions a person carries on 1 gene

Question 3

mendels research approach

Answer 3

1. studies pea plants (ideal organism)
2. pea plants have many easily categorized traits
3. distinct populations were established (repeated breeding)

Question 4

why were pea plants ideal

Answer 4

1. only 2 versions of alleles
2. easy to grow and control environments
3. grow and reproduce quickly
4. lots of offspring
5. easy to manipulate (self-fertilizing and cross-fertilize)

Question 5

cross

Answer 5

process in which male pollen is used to fertilize egg

Question 6

true-breeding

Answer 6

a population of organism where, for a given trait, the offspring of crosses of individuals within population always shows the same trait

Question 7

dominant

Answer 7

masks effect of a recessive trait when organism carries both traits

Question 8

recessive

Answer 8

allele masked by dominant allele for that trait

Question 9

3 ideas for patterns of inheritance

Answer 9

1. rather than passing on trait itself, each parent puts into every sperm/egg it makes a single set of instructions for building trait (gene)
2. offspring receive 2 copies of instructions for any trait
3. trait observed in an individual depends on 2 copies of the gene it inherits from its parents

Question 10

homozygous

Answer 10

genotype of a trait for which the 2 alleles an organism carries are the same

Question 11

heterozygous

Answer 11

genotype of a trait for which 2 alleles of an organism are different

Question 12

mendel’s law of segregation

Answer 12

principle that during the formation of gametes, the 2 alleles for a gene separate, half gametes carry one allele, other half carry other allele

Question 13

phenotype

Answer 13

outward appearance and behavior of an individual

Question 14

genotype

Answer 14

genetic composition

Question 15

Punnett square

Answer 15

help identify possible outcomes for crosses between 2 individuals

Question 16

test-cross

Answer 16

mating where a homozygous recessive individual is bred with individuals with dominant phenotype

Question 17

pedigrees

Answer 17

type of family tree that maps out the occurrence of a trait in a family, often over many generations

Question 18

sex-linked traits

Answer 18

traits controlled by genes on sex chromosomes

Question 19

carrier

Answer 19

individual who carries 1 allele for a recessive trait and does not exhibit the trait

Question 20

incomplete dominance

Answer 20

phenotype of heterozygous is intermediate between phenotypes of the 2 homozygotes

Question 21

codominance

Answer 21

heterozygous displays characteristics of both homozygotes
- white chicken and black chicken make black and white chicken

Question 22

multiple allelism

Answer 22

single gene has more than 2 alleles (within a population)

Question 23

antigens

Answer 23

chemical on surface of some cells: tell body if cell is supposed to be there

Question 24

antibodies

Answer 24

immune system molecules that attack cells with foreign antigens

Question 25

polygenic

Answer 25

trait influenced by many genes

Question 26

additive effects

Answer 26

effects from alleles of multiple genes that all contribute to the ultimate phenotype for a given characteristic
- variation in hight, eye color, behavioral traits

Question 27

pleiotrophy

Answer 27

phenomenon in which an individual gene influences multiple traits

Question 28

Mendel’s law of independent assortment

Answer 28

1 trait doesn’t influence inheritance of another trait

Question 29

dihybrid

Answer 29

individual that is heterozygous at 2 genetic loci

Question 30

dihybrid cross

Answer 30

cross btwn 2 individuals that are heterozygotes for the same 2 genetic loci

Question 31

linked genes

Answer 31

genes are close to each other on a chromosome and are more likely to be inherited together