Single Gene Autosomal Inheritance

Question 1

what are genes? where are genes located? what are genes made of? what do genes retain?do genes vary between individuals?

Answer 1

the hereditary units in which parents give their offspring coded information
-genes are located on chromosomes
-genes are made of a specific sequence of DNA nucleotides
-Genes retain their separate identities within an
individual = no blending occurs
-combination of genes varies between individuals

-discrete heritable unit

Question 2

what is the function of most genes?

Answer 2

to direct cells to synthesize a specific protein that results in an inherited trait

Question 3

what is an autosome?

Answer 3

-any chromosome other than a sex chromosome

Question 4

what is autosomal inheritance?

Answer 4

-inheritance of genes carried on the autosomes

Question 5

what is a sex chromosome? which chromosomes are these in humans?

Answer 5

chromosomes that differ in number between the different sexes
-X and Y chromosomes in humans

Question 6

what is sex linked inheritance?

Answer 6

inheritance of genes on the sex chromosomes, usually X chromosome in humans

Question 7

1 chromosome contains what? the specific location of one of theses is called what?

Answer 7

100s-1000s of genes

-Specific location of a gene on a chromosome = locus

Question 8

what is a particular version of a gene? how many of these do most genes have?

Answer 8

an allele

• most genes have two or more alleles
  e. g. flower-color gene: purple allele & white allele

Question 9

For each gene, how many alleles does a diploid organism inherit? if 2 alleles at a particlar gene are identical, what are they called? if they differ, what are they called?

Answer 9

2 alleles –> one from each homologous chromosome

• identical = homozygous
• differ = heterozygous

Question 10

what does the dominant allele determine in a gene that is heterozygous? what does the recessive gene detemine?

Answer 10

• the appearance

- recessive gene has no effect on appearance

Question 11

what is genotype?

Answer 11

the genetic make-up of an organism;

pair of alleles for a particular gene

Question 12

what is homozygous?

Answer 12

organism with two identical alleles for a particular gene

Question 13

what is heterozygous?

Answer 13

organism with two different alleles for a particular gene

Question 14

what is phenotype?

Answer 14

visible characteristic of an organism

Question 15

what is the dominant allele? how is it represented?

Answer 15

is the allele that is fully expressed in the phenotype of a heterozygote
-represented by capital letter

Question 16

what is the recessive allele? how is it represented?

Answer 16

is the allele that is not expressed in the phenotype of a heterozygous individual
-reprsented by lower-case letter

Question 17

what did Mendel’s experiment study?

Answer 17

• studied characteristics that varied between 2 distinct alternatives
• crossed 2 pure bred varieties with different alleles at one gene to create hybrid offspring - monohybrid cross

Question 18

what is True-breeding? what generation are these? are they homozygous or heterozygous?

Answer 18

plants bred with homozygous lines, which produce plants with the same phenotype for many generations
-e.g. all purple flowers for many generations

Parent generation –> P generation
homozygous

Question 19

what is a monohybrid cross? what generation are these? are they homozygous or heterozygous?

Answer 19

offspring that results from two pure-breeding varieties with different alleles at one gene
e.g. homozygous purple-flowered plants crossed
with homozygous white-flowered plants

Hybrid (heterozygous) offspring –> F1 generation

Question 20

what is the generation breed from hybrids? are they homozygous or heterozygous?

Answer 20

Offspring from cross between F1s = F2 generation

-heterozygous

Question 21

which was the dominant allele in F1 generation?

Answer 21

purple allele was dominant
-Genetic contribution from the white-flowered parent
is not visible in F1 plants

Question 22

what is a Punnett Square?

Answer 22

diagram used to predict allele composition of offspring from cross between individuals of known genotype

Question 23

when did White-flower color reappear?what did this prove?

Answer 23

White-flower color reappears in F2 generation
-Proved that allele for white color was present in F1
but was not having an affect on the petal color

Question 24

what were the 3 main findings of mendel’s experiments?

Answer 24

1. F1 generation all looked like one of P plants
2. Recessive trait reappeared in F2 generations
3. 3:1 phenotypic ratio in F2 generation

Question 25

what is the genotypic ratio?

Answer 25

the ratio of allele composition in F2 generation

eg. 1 PP (homozygous dominant), 2 Pp (heterozygous), 1 pp (homozygous recessive)

Question 26

what is phenotypic ratio?

Answer 26

ratio of which phenotypes appear in F2 generation

eg. 3 purple, 1 white