Chapter 11 inheritance

Question 1

Inheritance

Answer 1

is the process by which the traits of organisms are passed to their offspring.

Question 2

alleles

Answer 2

are slightly different nucleotide sequences of a gene in a certain species. as per a result of a mutation or error in replicating DNA.

Question 3

mutations

Answer 3

changes in the sequence of nucleotides in the DNA of a gene. If a mu- tation occurs in a cell that becomes a sperm or egg, it can be passed on from parent to offspring. all alelles originated as mutations and were passed down generations.

Question 4

If both homologues have the same allele at a given

gene locus, the organism is said to be

Answer 4

homozygous

Question 5

If two homologous chromosomes have different alleles at a locus, the organism is _____ (“different pair”) at that locus.

Answer 5

heterozygous

Question 6

genotype

Answer 6

the genetic composition of an organism: the actual alleles of each gene carried by the organism

Question 7

phenotype

Answer 7

the physical characteristics of an organism; can be defined as outward appearance, behaviour or molecular characteristics

Question 8

dominant

Answer 8

an allele that can determine the phenotype of heterozygotes so that they are indistinguishable from individuals homozygous for that allele. The expression of the other, recessive allele is completely masked

Question 9

recessive

Answer 9

an allele that is expressed only in homozygotes and is completely masked in heterozygotes in the presence of a dominant allele

Question 10

howdid Mendel’s experimentscontributed to our understanding of inheritance of a single gene.

Answer 10

Mendel discovered the fundamental laws of inheritance. He deduced that genes come in pairs and are inherited as distinct units, one from each parent. Mendel tracked the segregation of parental genes and their appearance in the offspring as dominant or recessive traits.

Question 11

segregation

Answer 11

the process in eukaryotes by which two sister chromatids formed as a consequence of DNA replication, or paired homologous chromosomes, separate from each other and migrate to opposite poles of the nucleus. This process occurs during both mitosis and meiosis.

Question 12

Autosomes:

Answer 12

a chromosome that occurs in homologous pairs in both males and females and that does not bear the genes determining sex

Question 13

Independent assortment:

Answer 13

where the alleles of two (or more) different genes get sorted into gametes independently of one another; they are not linked

Question 14

Punnet square:

Answer 14

a method of predicting the genotype and phenotype of offspring in genetic crosses

Question 15

Test cross:

Answer 15

a breeding experiment in which an individual showing the dominant phenotype is mated with an individual that is homozygous is recessive for the same gene.

Question 16

Incomplete dominance:

Answer 16

a pattern of inheritance in which the heterozygous phenotype is intermediate between the two homozygous phenotypes

Question 17

Pleiotropy:

Answer 17

the situation in which a single gene influences more than one phenotypical characteristic

Question 18

Sex-linked:

Answer 18

referring to a pattern of inheritance characteristic of genes located on one type of sex chromosome and not found on the other type. For instance in X linked inheritance, females show the dominant trait unless they are homozygous recessive, whereas males express whichever allele, dominant or recessive is found on their X chromosome