Genetics Vocabulary

Vocabulary Word DefinitionOther Things to Know… Genetics The field of Biology devoted to understanding how traits are passed from parents to offspring Gregor Mendel -pioneer in genetics -crossed peas to show how traits were passed on

Gregor Mendel ( )  Austrian monk  Called the “Father of Genetics" for his study of the inheritance of 7 traits in pea plants.

Gregor Mendel ( ) The traits that Mendel chose to study were easily observable in 2 distinct forms. EX.: Stem Height - tall vs. short Pod Shape - round vs. wrinkled Flower Color – white vs. purple Seed Color – green vs. yellow

Gregor Mendel ( )  The significance of Mendel's work was not recognized until the turn of the 20 th century  Its rediscovery prompted the foundation of genetics.

Vocabulary Word DefinitionOther Things to Know… Heredity The transmission of traits from parents to their offspring Important for understanding reasons for our appearance and study of genetic diseases

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

Vocabulary Word DefinitionOther Things to Know… Trait A category within which alternate characteristics can be observed Examples of traits: hair color, eye color, height

Vocabulary Word DefinitionOther Things to Know… Gene A segment of DNA that contains coding for a polypeptide or protein – a unit of hereditary information Found on chromosomes within the nucleus

vocabulary terms HOMOLOGOUS CHROMOSOME- A pair of matching chromosomes in an organism, with one being inherited from each parent.

vocabulary terms AUTOSOME- A chromosome that is not a sex chromosome.

Vocabulary Word DefinitionOther Things to Know… Alleles An alternate form of a gene Ex: Everyone has an eye color, but there are different types: blue, brown, etc.

vocabulary terms 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 (P) (p)

Vocabulary Word DefinitionOther Things to Know… Dominant An allele that masks the presence of another allele for 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 BbRecessive: bb ONLY

What are Dominant Genes? Hereford: white face is dominant Dominant: WW or WwRecessive: ww ONLY

Vocabulary Word DefinitionOther Things to Know… Recessive An allele that is masked by the presence of another allele for the same characteristic -Shown with a lower case letter (ex: a, t, g). -Will only be seen if both alleles for a trait are recessive.

What are Recessive Genes? Black wool is recessive to white wool. Dominant: WW or WwRecessive: ww ONLY

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

Vocabulary Word DefinitionOther Things to Know… Law of Segregation Law stating that pairs of genes separate in meiosis and each gamete receives one gene of a pair Allows each parent to contribute half the chromosomes to produce offspring with the full # of chromosomes.

Vocabulary Word DefinitionOther Things to Know… Law of Independent Assortment Law stating that pairs of genes separate independently of one another in meiosis The gene for eye color sorts separately from hair color, and skin color, etc…

Vocabulary Word DefinitionOther Things to Know… Genotype The genetic makeup of an organism Written with the letters of alleles: Aa, TT, bb, etc.

vocabulary terms 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

vocabulary terms Now, it turns out there are 3 possible GENOTYPES: TT = homozygous = purebred Tt = heterozygous = hybrid tt = homozygous = purebred

Vocabulary Word DefinitionOther Things to Know… Phenotype The external (physical) appearance of an organism that is determined by the individual’s genotype Written as the Physical 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 DefinitionOther Things to Know… Homozygous Referring to a gene pair in which the two alleles code for the same trait Written as: AA or aa

Vocabulary Word DefinitionOther Things to Know… Heterozygous Referring to a gene pair in which the two alleles do not code for the same trait Written as: Aa

Vocabulary Word DefinitionOther Things to Know… Purebred An organism that is homozygous for a trait Ex: AA or aa

Vocabulary Word DefinitionOther Things to Know… Hybrid An organism that is heterozygous for a trait Ex: Aa

Genotype Symbol Genotype Vocabulary Phenotype TT homozygous DOMINANT or purebred tall tall Tt heterozygous or hybrid tall tt homozygous RECESSIVE or purebred short short

Vocabulary Word DefinitionOther Things to Know… Probability The number of times an event is expected to happen divided by the number of opportunities of an event to happen Ex: dice, coin-flipping, chance of have blue 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 DefinitionOther Things to Know… Punnett Square A model used to establish the probabilities of the results of a genetic cross Mom’s alleles go together on one side and Dad’s go together on 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. P p P PP p pp PP p p Homozygous- recessive Homozygous- dominant

PP p Pp p These results show that all the F 1 (1 st filial generation) offspring are all purple colored hybrids. 100% purple offspring

PPP Pp p p p Pp P p We can use another Punnett square to predict the F 2 (2 nd filial generation) offspring. Heterozygous - hybrid

PPP Pp p p p Pp P p The results are always mathematically the same, a 3:1 ratio with 75% purple & 25% white offspring Heterozygous - hybrid Phenotypic ratio 3:1 Genotypic ratio 1:2:1