Topic 12.1: Nomenclature

Question 1

what is genotype

Answer 1

the genetic make up
the DNA sequence of an organism or individual which determines the specific characteristics (phenotype) of that organism or person

Question 2

what is phenotype

Answer 2

the characteristics
an organism’s observable physical and biochemical characteristics directly influenced by the genotype and/or environment. the observed signs and symptoms of a condition

Question 3

how many copies of each gene do each individual ahve

Answer 3

2

Question 4

how many alleles of a gene does a person have

Answer 4

2

Question 5

what is a gene

Answer 5

a stretch of DNA sequence at a specific chromosomal location that carries the code for a polypeptide or untranslated RNA (plus regulatory sequences)

Question 6

what is an allele

Answer 6

a version or variant of a gene

Question 7

what are the genes like in homologous chromosomes

Answer 7

homologous chromosomes have the same genes but may carry different alleles

Question 8

what are the genes like in sister chromatids

Answer 8

sister chromatids have identical DNA and the same alleles

Question 9

what are the genes like in non-sister chromatids

Answer 9

they have the same genes but may have different alleles

Question 10

what does homozygous mean

Answer 10

two alleles of a gene are the same

individual is known as homozygote

Question 11

what does heterozygous mean

Answer 11

two alleles of a gene are different

individual is known as heterozygote

Question 12

what does hemizygous mean

Answer 12

only one allele of a gene on the X chromsome

Question 13

what does dominant mean

Answer 13

the dominant allele in a heterozygote determines the phenotype

Question 14

what does recessive mean

Answer 14

the non dominant allele in a heterozygote

Question 15

what does co dominant mean

Answer 15

neither allele in a heterozygote is dominant and the phenotype is new (different from phenotypes determined by either allele)

Question 16

where is the gene located for human bloody types and what does it code for

Answer 16

on chromosome 9 and codes for glycoproteins on the surface of red blood cells

Question 17

how is the gene for blood types often written as

Answer 17

I

Question 18

what are the different alleles for blood type

Answer 18

A, B and O or I^A, I^B, I^O
alleles A and B are dominant over O
alleles A and B are co dominant

Question 19

what are the 4 phenotypes for blood types

Answer 19

A, B, AB, O

Question 20

what are the genotypes for blood group A

Answer 20

I^A I^A
OR
I^A I^O

Question 21

what are the genotypes for blood group B

Answer 21

I^B I^B
OR
I^B I^O

Question 22

what are the genotypes for blood group AB

Answer 22

I^A I^B

Question 23

what are the genotypes for blood group O

Answer 23

I^O I^O

Question 24

what are the symbols for pedigree analysis

Answer 24

male = square
female = circle
affected = filled in
heterozygote = half filled
carrier female = outer white circle and black dot in middle
unknown sex = diamond
deceased = line through symbol
same kinship = two lines between square and circle
married = one line between square and circle
monozygotic twins = two circle attached with triangle and inner triangle
dizygotic twins = two circles attached with triangle
two diagonal lines through relationship = divorce
square with D = donor
generations with roman numerals, and number of birth is another number

Question 25

what are important features of pedigree analysis

Answer 25

every generation on separate line
label every generation with roman numerals, top to bottom
males left and females right in relationship where possible
siblings in age order, from left to right
label every individual of every generation with numbers, left to right
shading indicates phenotype