Classical Genetics Flashcards Preview

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Flashcards in Classical Genetics Deck (35):
1

Law of Dominance

When 2 organisms, each homozygous (pure) for 2 opposing traits are crossed, the offspring will be hybrid (carry out 2 different alleles) but will exhibit only the dominant trait
Trait that remains hidden = recessive trait

2

Law of Segregation

When an organism makes gametes, each gamete receives just 1 copy, which is selected randomly

3

Monohybrid cross

A cross between 2 organisms that are each hybrid for a single trait
(Tt x Tt)

4

Genotype

Type of gene
The set of genes in DNA which is responsible for a particular trait
Genes responsible for: eye colour, height, shoe size

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Phenotype

What an organism looks like
The visible expression/characteristics of that trait
Visible characteristics for; eye colour, height, shoe size

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Backcross (Testcross)

A technique to determine whether an individual plant or animal showing the dominant trait is homozygous dominant (BB) or heterozygous (Bb)

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Incomplete Dominanc

An inheritance pattern characterised by blending of traits
Black animal cross with white animal = grey offspring

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Law of Independent Assortment

A cross that is carried out between 2 individuals hybrid for 2 or more traits that are not on the same chromosome
Resulting phenotype ratio: 9:3:3:1

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Codominance

When the alleles of a gene are expressed equally & neither is dominant or recessive
Blood type; A & B -> AB

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Multiple Alleles

When there are more than 2 allelic forms of a gene
Humans, more than 2 alleles for blood type

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Polygenic

More than 2 allelic forms of a gene, like height or colour, the trait exhibits a multitude of variation
Two short parents -> tall offspring

12

Sex-Linked

Traits that are carried on the X chromosome
Recessive traits: colour blindness, haemophilia

13

Sex-Influenced Trait

Inheritance is influenced by sex of individual carrying the traits
Baldness

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Karyotype

Procedure that analyses the size, shape, & number of chromosomes
During metaphase of mitosis

15

Pedigree

Family tree that indicates the phenotype of 1 trait being studied for every member of a family
Used to determine how a particular trait is inherited

16

Mutation

Any change in a gene or chromosome, when/where mutations occur is random

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Gene Mutations

Caused by a change in the DNA sequence

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Chromosome Mutations

Chromosome may sustain a deletion/addition, or cell may have an entirely extra chromosome which results from nondisjunction

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Nondisjunction

An error that sometimes happens during meiosis in which homologous chromosomes fail to separate as they should

20

Aneuploidy

Any abnormal condition of the chromosomes

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Deletion

A fragment lacking a centromere is lost during cell division

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Inversion

A chromosomal fragment reattaches to its original chromosome but in the reverse orientation

23

Translocation

A fragment of a chromosome becomes attached to a non-homologous chromosome

24

Polyploidy

A cell/organism that has extra sets of chromosomes
Often plants or flowers

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Gene

Heritable factor that controls a specific characteristic

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Allele

1 specific form of a gene, occupying the same gene locus as other alleles of the gene

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Genome

The whole of the genetic information of an organism

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Homologous Chromosomes

Chromosomes that have the same structural features & the same genes

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Dominant Allele

An allele that is expressed in the phenotype in a homozygous or heterozygous state

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Recessive allele

An allele that is only expressed in the phenotype in a homozygous state

31

Codominant Alleles

A pair of alleles which both affect the phenotype in a heterozygous

32

Homozygous

Having 2 identical alleles of a gene

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Heterozygous

Having 2 different alleles of a gene

34

Carrier

A heterozygote who has 1 copy of a recessive allele that causes a genetic disease

35

Autosome

Any chromosome that is not a sex linked chromosome