Genetics Vocabulary

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Genetics Vocabulary

Vocabulary Word

Definition Other Things to Know…

Genetics

The field of Biologydevoted to understanding how traits are passed from parents to offspring

Gregor Mendel-pioneer in genetics-crossed peas toshow how traitswere passed on

Gregor Mendel (1822-1884)

Austrian monk

Called the “Father of Genetics" for his study of the inheritance of 7 traits in pea plants.

The traits that Mendel chose to study were easily observable in 2 distinct forms.

EX.: Stem Height - tall vs. shortPod Shape - round vs. wrinkledFlower Color – white vs. purpleSeed Color – green vs. yellow

The significance of Mendel's work was not recognized until the turn of the 20th century

Its rediscovery prompted the foundation of genetics.

Vocabulary Word

Heredity

The transmission oftraits from parents to their offspring

Important for understanding reasons for ourappearance andstudy of geneticdiseases

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INHERITANCE or HEREDITY- The genetic transmission of characteristics from parent to offspring, such as hair, eye, and skin color.

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A category withinwhich alternatecharacteristics can be observed

Examples of traits:

hair color, eye color,

height

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A segment of DNAthat contains codingfor a polypeptide orprotein – a unit of hereditary information

Found on chromosomes within the nucleus

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HOMOLOGOUS CHROMOSOME-

A pair of matching chromosomes in an organism, with one being inherited from each parent.

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AUTOSOME-A chromosome that is not a sex chromosome.

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Alleles

An alternate formof a gene

Ex: Everyonehas an eye color,but there are different types:blue, brown, etc.

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ALLELES- alternative forms of the same gene. Alleles for a trait are

located at corresponding positions on homologous chromosomes called loci.

A b C d e

A B c d E

Chromosome from MOM

Chromosome from DAD

ALLELES

Chromosome from MOM: p

Chromosome from DAD: P

Vocabulary Word

Dominant

An allele that masksthe presence ofanother allelefor the same characteristic

-Shown with a capital letter(ex: A, T, G).-Will always be seen if present.

What are Dominant Genes? Dominant Genes = one gene

overshadows the other Angus Cattle: black is dominant,

red is not

Dominant: BB or Bb Recessive: bb ONLY

What are Dominant Genes?Hereford: white face is dominant

Dominant: WW or Ww

Recessive: ww ONLY

Vocabulary Word

Recessive

An allele that is masked by the presence of anotherallele for the samecharacteristic

-Shown with a lower case letter(ex: a, t, g).-Will only be seen if both alleles for a traitare recessive.

What are Recessive Genes?

Black wool is recessive to white wool.

Dominant: WW or Ww

Recessive: ww ONLY

What are Recessive Genes? Albinism (Albino) is recessive to

pigmented.

Vocabulary Word

Law ofSegregation

Law stating that pairs of genes separate in meiosisand each gamete receives one gene of a pair

Allows each parent to contribute half thechromosomes to produce offspringwith the full # ofchromosomes.

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Law ofIndependentAssortment

Law stating that pairs of genesseparate independently of one another in meiosis

The gene for eye color sorts separately from hair color, and skin color, etc…

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Genotype

The genetic makeupof an organism Written with the

letters of alleles:

Aa, TT, bb, etc.

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GENOTYPE- the genes present in the DNA of an organism.

There are always 2 letters in the genotype because (as a result of

sexual reproduction) 1 gene from MOM + 1 gene from DAD

= 2 genes (2 letters) for offspring

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Now, it turns out there are 3 possible GENOTYPES:

TT = homozygous = purebred Tt = heterozygous = hybrid

tt = homozygous = purebred

Vocabulary Word

Phenotype

The external (physical)appearance of an organism that is determined by theindividual’s genotype

Written as thePhysical Trait:

Brown hair, blue eyes, short, etc.

vocabulary terms

PHENOTYPE- how the trait physically shows-up in the organism; it is the observable traits present in an organism What the organism LOOKS like

Examples of phenotypes: blue eyes, brown fur, striped fruit, yellow flowers

Vocabulary Word

Homozygous

Referring to a genepair in which the two alleles code for the same trait

Written as:AA or aa

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Heterozygous

Referring to a genepair in which the two alleles do notcode for the same trait

Written as: Aa

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Purebred

An organism that ishomozygous for a trait

Ex: AA or aa

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Hybrid

An organism thatis heterozygous for a trait

Ex: Aa

Genotype Symbol

Genotype Vocabulary

Phenotype

TThomozygous DOMINANT

or purebred

Ttheterozygou

hybrid

tthomozygous RECESSIVE

or purebred

Vocabulary Word

Probability

The number of timesan event is expectedto happen dividedby the number of opportunities of an event to happen

Ex: dice, coin-flipping, chance of haveblue eyes, etc.

Geneticists apply mathematical principles of probability to Mendel’s laws of heredity in order to predict the results of simple genetic crosses

Mendel’s laws of heredity are based

on his mathematical analysis of observations of patterns of the inheritance of traits.

The laws of probability govern simple genetic recombinations.

To see this we use a Punnett Square

Vocabulary Word

PunnettSquare

A model used to establish the probabilities of theresults of a geneticcross

Mom’s allelesgo together on one side and Dad’s go togetheron the other.

Punnett Squares

• For the pea plant flowers:

dominant: purple color = P

recessive: white color = p.

• If both parents are purebred, then

the purple colored parent must be

PP and the white colored parent

must be pp.

How can we predict these

results?

We complete the

possible combinations.

pHomozygous-

recessive

Homozygous-dominant

p Pp Pp

These results show that all the

F1 (1st filial generation) offspring

are all purple colored hybrids.

100% purple offspring

We can use another

Punnett square to

predict the F2 (2nd

filial generation)

offspring.Heterozygous - hybrid

Heterozygous - hybrid

The results are

always

mathematically the

same, a 3:1 ratio

with 75% purple &

25% white

offspringHeterozygous - hybrid

Heterozygous - hybrid

Phenotypic ratio 3:1Genotypic ratio 1:2:1

Genetics Vocabulary

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