Chapter 3.2: The Cell, DNA, and Mendelian Genetics

Deoxyribonucleic Acid (DNA)

• Matching strands in a double helix

• Backbone of Phosphate and Sugar

• Inner links are pairs of nucleotides/bases

Bases/Nucleotides in DNA

• Adenine (A)

• Guanine (G)

• Cytosine (C)

• Thymine (T)

What Base/Nucleotides Pairs With Which?

• (A) → (T)

• (C) → (G)

Alphabet (In terms of DNA)

4 repeating letters in any number of possible forms.

DNA Stability

• Stable Molecule

• Read & replication of DNA reliably

• 1 mistake/billion BPs

Steps of DNA Replication

1. Inner links detach from each other (Unzips)

2. New strands attach to old strands via inner link (Bases)

3. Original strands completely separate, creating 2 new DNA molecules

4. Enzymes proofread new strands

Gene

Segment of DNA that makes a functional product; segregates as a unit during gamete formation; makes protein.

How Are Genes Arranged?

Arranged on chromosomes at a specific point (Locus)

Locus

A specific point where a gene lies in a chromosome.

Alleles

Variations of a Gene.

DNA Encoding

• If there are differences in the DNA sequencing, then there will be variations in the traits

• Some DNA codes for proteins, and some DNA codes for regulatory sequences

Gene Composition

• Introns (non-coding)

• Exons (Coding)

What Two Types of Protein Does DNA Sequence Code For?

• Enzymes

• Non-Enzymatic Proteins

Enzymes

Catalyze chemical reactions in cells.

Codons

Pairs of amino acids grouped in triplets.

What do Proteins Consist of?

Chains of amino acids (PRIMARY STRUCTURE) that fold in to complex 3D shapes (TERTIARY STRUCTURE)

Sequence of Codons

The sequence of codons determines the sequence of amino acids.

Redundancy/Synonymous Substitution

Protects against deleterious changes in protein structure caused by DNA damaged

How is Genetic Info Organized? Give An Example

1. Genome (Book)

2. Chromosome (Chapter)

3. Gene (Sentence)

4. Base Pair (Letter)

Regulatory Sequences

DNA sequences that determine if/when protein-coding sequences are expressed.

How Do Regulatory Sequences Affect Cells?

Every cell has the same DNA, regulatory sequences determine which genes to turn off for each cell.

Gene Regulation

Allows for cell differentiation from single-cell zygote.