Lecture 12

Question 1

what are genes

Answer 1

a segment of DNA that influences the structure & function of an organism by encoding & directing the synthesis of mRNA, tRNA, rRNA & ultimately a polypeptide

Question 2

allele ?

Answer 2

One of two or more variants of a gene pair that occur at the same locus. A diploid individual inherits two alleles for each gene, one from each parent
Alleles can be dominant, recessive, co-dominant, or show incomplete dominance.

Question 3

genotype?

Answer 3

We call the allelic composition of an individual, the genotype

Question 4

phenotype?

Answer 4

the appearance, or the characteristics, the phenotype.

Question 5

how many gens do humans have ?

Answer 5

somewhere between 21,000-25,000

Question 6

genome?

Answer 6

The complete complement of an organisms’ genes and non-gene DNA ie all the DNA in an organism.

Question 7

correct order of organization of genetic material, from largest to smallest?

Answer 7

Genome, chromosome, DNA, gene, nucleotide

Question 8

how did Mendel figure out genetics

Answer 8

Lots of pea plants & math

Nothing was known about meiosis
& genes weren’t even discovered yet!

Question 9

how did Mendel do the crossings

Answer 9

P generation: were always true breeders

Parent x Parent → F1 generation

F1 x F1 → F2 generation Crossed F1 with itself to get the F2 generation

Question 10

Mendel’s model of inheritance

Answer 10

1. There are alternate versions of genes (alleles)
2. For each character: an organism inherits 2 alleles, 1 from each parent
3. If the 2 alleles at a locus differ: the dominant allele determines the organism’s appearance
4. 2 alleles separate (segregate) during meiosis & end up in different gametes ie each parent passes on 1 copy (not 2) of each allele.

Question 11

Recall the life cycle

Answer 11

adult → meiosis → sperm or egg → fertilization → mitosis → embryo → mitosis → fetus → mitosis → child to adult.

Question 12

Character?

Answer 12

A feature that can be inherited. Ex hair color

Question 13

Trait?

Answer 13

A specific version of a character. Ex RED hair

Question 14

_ are to genes as traits are to alleles.

Answer 14

Characters

Question 15

Gene locus

Answer 15

a specific place along the chromosome where a given gene is located. Genes are arranged in a fixed order along the chromosome

Question 16

Autosomes

Answer 16

The chromosomes other than the sex chromosomes

Question 17

Homologous chromosomes

Answer 17

a pair of chromosomes that carry genes for the same characters at corresponding loci. The alleles at each locus may be the same or different

Question 18

Dominant allele

Answer 18

an allele of a gene whose expression is observable in a heterozygote. ; the phenotype of the heterozygote (ex Tt) is indistinguishable from that of the dominant homozygote (TT).

Question 19

Recessive allele

Answer 19

an allele whose expression is observable only in the homozygous form (tt), ie when the dominant allele is absent.

Question 20

Law of independent assortment

Answer 20

Mendel’s second law holds that during gamete formation, genes for different traits are separated from each other independently during meiosis
random line up of chromosomes during metaphase I which results in each member of a pair of homologous chromosomes separating independently of the other chromosomes during anaphase

Question 21

Mendel discovered the Law of independent assortment based on the analysis of his ___.

Answer 21

dihybrid crosses

Question 22

Law of segregation?

Answer 22

a diploid organism passes a randomly selected allele for a trait to its offspring, such that the offspring receives one allele from each parent.

Question 23

Mendel discovered the Law of segregation based on the analysis of his __

Answer 23

monohybrid crosses.

Question 24

Monohybrid cross

Answer 24

cross parents that are true-breeders (homozygous) for the character you’re studying that differ at 1 locus

Question 25

ratio of Monohybrid cross?

Answer 25

3:1

Question 26

dihybrid cross?

Answer 26

study of inheritance patterns for organisms differing in two traits of interest.

Question 27

ratio Dihybrid cross

Answer 27

9:3:3:1

Question 28

Punnett square?

Answer 28

a diagram that is used to predict the probable outcome of a particular genetic cross. The diagram is used to determine the probability of an offspring having a particular genotype.

Question 29

Carrier

Answer 29

An individual who has a recessive, disease-causing allele at a particular locus on one chromosome of a pair and a normal allele at that locus on the other chromosome (ex if N=normal, n=disease then a carrier would be Nn) AND this individual is phenotypically normal

Question 30

which one is more specific? trait or character?

Answer 30

trait

Question 31

what % of dna is genes

Answer 31

les than 2%

Question 32

True breeders?

Answer 32

Homozygous for a specific character

Question 33

3 possible genotypes

Answer 33

Homozygous dominant: YY

Homozygous recessive: yy

Heterozygous: Yy

Question 34

Monohybrids criteria

Answer 34

(1) One character
(2) homozygous (AA or aa)
(3) 2 parents must differ (AA x aa, not AA x AA)

Question 35

Albinism: A _____ disorder

Answer 35

recessive

Question 36

Huntington’s disease: A _____ disorder

Answer 36

dominant

Question 37

Achondroplasia: a __trait

Answer 37

dominant

Question 38

do one of the parents must have the disorder if it is dominant?

Answer 38

yes.

Question 39

do one of the parents must have the disorder if it is recessive?

Answer 39

no, they can be heterozygote.