SET 7 – TEAS 7 Genetics, DNA, and Punnett Squares

DNA

Double-stranded molecule carrying genetic instructions

RNA

Single-stranded molecule used in protein synthesis

Chromosome

Tightly coiled DNA found in nucleus

Gene

Segment of DNA coding for a trait

Allele

Different form of a gene (ex: A or a)

Genotype

Genetic makeup (letter combination)

Phenotype

Physical trait expressed

Dominant allele

Expressed even with one copy (A)

Recessive allele

Expressed only with two copies (aa)

Homozygous dominant

AA genotype

Homozygous recessive

aa genotype

Heterozygous

Aa genotype

Punnett square

Diagram used to predict offspring traits

Probability

Likelihood of trait appearing

Codominance

Both alleles expressed equally (ex: AB blood type)

Incomplete dominance

Blended phenotype (red + white = pink)

Autosomes

Non-sex chromosomes

Sex chromosomes

X and Y chromosomes determining biological sex

XX

Female genotype

XY

Male genotype

Sex-linked trait

Trait carried on X chromosome

X-linked recessive

More common in males

Mutation

Change in DNA sequence

Substitution mutation

One nucleotide replaced by another

Deletion mutation

Piece of DNA is removed

Insertion mutation

Extra nucleotide added

Frame-shift mutation

Alters reading frame; big effect on protein

DNA replication

DNA copying itself before cell division

Helicase

Enzyme that unwinds DNA

DNA polymerase

Enzyme that builds new DNA strand

Transcription

DNA to mRNA

Translation

mRNA to protein

mRNA

Messenger RNA carrying DNA code

tRNA

Transfers amino acids to ribosome

Ribosome

Site of protein synthesis

Amino acid

Building block of proteins

Protein

Final product of gene expression

Gene expression

Gene converted into protein

Nucleotide

Building block of DNA (sugar, phosphate, base)

Adenine

Pairs with thymine

Thymine

Pairs with adenine

Cytosine

Pairs with guanine

Guanine

Pairs with cytosine

Uracil

RNA base that replaces thymine

DNA backbone

Sugar-phosphate structure

Double helix

Twisted ladder shape of DNA

Replication fork

Area where DNA is split and copied

Chromatid

One copy of a duplicated chromosome

Centromere

Region where chromatids attach

Karyotype

Chromosome picture used to detect abnormalities

Trisomy

Extra chromosome (ex: Down syndrome)

Monosomy

Missing chromosome

Natural selection

Organisms with beneficial traits survive and reproduce

Adaptation

Trait improving survival or reproduction

Evolution

Change in population over generations