Lab 5 Flashcards
Metacentric
The centromere in located in the middle of the chromosome
Subterminal
The centromere is located between the middle and the end of the chromosome
Acrocentric
The centromere is located very close to one end of the chromosome
Autosomal chromosomes
Carry genes that affect somatic characteristics (such as hair colour)
Sex chromosomes
Responsible for determining the genetic sex of an individual.
X or Y
Females: XX
Males: XY
Karyotype
A laboratory-produced image that arranges the chromosomes into pairs according to size and centromere position.
It is usually prepared from a cell during mitosis metaphase.
Why is it necessary to prepare a karyotype?
In order to look for any abnormalities in chromosome number or structure.
Nondisjunction
The failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division.
Down syndrome
(aka Trisomy 21)
A genetic disorder where an individual has 3 copies of chromosome 21, rather than the usual 2 copies. It happens when the chromosomes fail to separate properly during meiosis.
Patau syndrome
(aka Trisomy 13)
A genetic disorder in which there are 3 copies rather than 2 of chromosome 13 in either the egg or sperm before conception.
Edwards symdrome
(aka trisomy 18)
A genetic disorder in which an individual has 3 copies of chromosome 18 rather than 2.
Turner’s syndrome
A genetic disorder in which a female only has 1 X chromosome rather than 2.
Klinefelter’s syndrome
A genetic condition in which a male is born with an extra X chromosome, resulting in XXY.
Cri-du-chat syndrome
A genetic disorder in which there is total or partial loss chromosome 5
Locus
The position of a gene on a chromosome
(Drawn as a small stripe on a chromatid)
Genotype
The genetic constitution of an organism.
It is the actual genes present on the chromosomes of an individual
Uses: AA, Aa , aa
Phenotype
The actual observed characteristics of an individual.
Is it the physical expression of a gene
Ex. Blue eyes, brown hair…etc.
Alleles
Alternate forms of the same gene (ex. A and a) found at the same locus on a homologous chromosomes.
This codes for different phenotypes.
Dominant allele
An allele which needs to be present on only one of the two homologous chromosomes in order to be expressed.
Expressed by the capital letter (ex. A)
AA and Aa are phenotypically identical e since the dominant A masks the alternate allele a.
Recessive allele
An allele which must be present on both members of a pair of homologous chromosomes in order to be phenotypically expressed. (aa)
Expressed by lowercase letter (ex. a)
Homozygous
Refers to the presence of identical alleles on homologous chromosomes.
i.e. AA or aa
Heterozygous
Refers to the presence of unlike alleles on homologous chromosomes.
i.e. Aa
First filial generation (F1)
The offspring resulting from the crossing of individuals of the parental generation.
Second filial generation (F2)
The offspring resulting from crossing members of the F1 generation among themselves.
