Grade 8: Genetics and Heredity

The characteristics of an organism are the result of ....____________

the inherited traits received from parents.

In humans, where is DNA located?

Nucleus

DNA are made up of 4 ______________________.

nucleotides

Dominate traits

the trait that always shows up

Recessive traits

the trait that disappears to background

Nucleotide complementary to thymine

adenine

Nucleotide complementary to guanine

cytosine

Heredity

passing of traits from parent to offspring

DNA is in the shape of ?

double helix (looks like a twisted ladder)

Phenotype

Physical appearance (what it looks like)

Genotype

2 letter combination of alleles (example: PP or Pp)

Gene

one set of instructions for an inherited trait

Allele

different forms of a gene that determine a characteristic

Dominant allele

designated by capital letter (P)

Recessive allele

designated by lower case letter (p)

Homozygous

2 dominant (PP) or 2 recessive (pp)

Heterozygous

1 dominant & 1 recessive designated by 1 capital & 1 lower case letter (Pp, Hh, Bb)

Co-Dominance

when more than one dominant allele exists and they end up in the same genotype, they share dominance (examples: blood type-AB, roan horse colors)

Mendel's Law 1: Law of Dominance

the dominant trait will always show if present

Mendel's Law 2: Law of Segregation

you get 1 allele from each parent;

for each gene, there are at least two alleles, one inherited from each parent.

Mendel's Law 3: Law of Independent Assortment

traits are not usually connected to other traits

Types of Mutations

Substitution

Insertion

Deletion

Deletion

base is left out

Substitution

wrong base is used

Insertion

extra base is added

Mutations can have 3 outcomes (results):

Beneficial

Harmful

No effect

Human body cells have_________ pairs of chromosomes.

23

Ratio of dominant to recessive traits discovered by Mendel

3 to 1

Characteristics

feature with various forms (examples: eye color; hair color)

Traits

(examples: blue/green/brown; black/brown/blonde)

Why did Mendel use pea plants?

-could self-pollinate and cross pollinate- so he could control parentage

- familiar

- easy to grow

- they grew fast