Genetics and Cell Division: DNA, RNA, Mitosis, and Meiosis

Nucleotide

The building block of nucleic acids; made of a sugar, phosphate group, and nitrogen base.

DNA (Deoxyribonucleic Acid)

Molecule that stores genetic information; double-stranded helix.

RNA (Ribonucleic Acid)

Molecule that helps make proteins; single-stranded.

Replication

Process by which DNA makes an identical copy of itself.

Transcription

Process of making mRNA from a DNA template.

Translation

Process where mRNA is decoded by tRNA to make a protein.

Codon

Three-base sequence on mRNA that codes for a specific amino acid.

Amino Acid

The building block of proteins.

DNA Nucleotide Components

Deoxyribose sugar, phosphate group, and nitrogen base (A, T, C, G).

RNA Nucleotide Components

Ribose sugar, phosphate group, and nitrogen base (A, U, C, G).

Complementary Base Pairs in DNA

Adenine pairs with Thymine, and Cytosine pairs with Guanine.

Complementary Base Pairs in RNA

Adenine pairs with Uracil, and Cytosine pairs with Guanine.

Bonds Holding DNA Strands Together

Hydrogen bonds between nitrogen bases.

DNA Backbone

Alternating sugar and phosphate groups.

Differences Between DNA and RNA

DNA is double-stranded, has deoxyribose, and thymine; RNA is single-stranded, has ribose, and uracil.

Similarities Between DNA and RNA

Both made of nucleotides, both have a sugar-phosphate backbone, both use A, C, and G bases.

DNA Shape

Double helix.

RNA Shape

Single strand.

mRNA (Messenger RNA)

Carries genetic code from DNA to the ribosome.

tRNA (Transfer RNA)

Brings amino acids to the ribosome during translation.

rRNA (Ribosomal RNA)

Makes up part of the ribosome where proteins are assembled.

DNA Replication

DNA unwinds, complementary bases pair, and two identical DNA molecules form.

Transcription (Process)

DNA is used to make an mRNA strand in the nucleus.

Translation (Process)

Ribosome reads mRNA codons and tRNA brings amino acids to build a protein.

Codon Chart/Wheel

Tool used to determine which amino acid each mRNA codon codes for.

Complementary DNA Strand Example

If DNA = ATCG, complementary = TAGC.

mRNA Transcription Example

If DNA = TACG, mRNA = AUGC.

tRNA Anticodon Example

If mRNA = AUG, tRNA = UAC.

Chromatin

Uncoiled DNA and proteins found in the nucleus.

Chromatid

One half of a duplicated chromosome.

Chromosome

Condensed, coiled DNA carrying genetic information.

Haploid

A cell with one set of chromosomes (n).

Diploid

A cell with two sets of chromosomes (2n).

Mitosis

Division of the nucleus to create identical body cells.

Meiosis

Division that produces gametes with half the number of chromosomes.

Somatic Cell

Any body cell except gametes.

Gametic Cell (Gamete)

Reproductive cell such as sperm or egg.

Homologous Chromosomes

Pairs of chromosomes, one from each parent, with the same genes.

Zygote

Fertilized egg formed from sperm and egg.

Prokaryote vs Eukaryote Division

Prokaryotes divide by binary fission; eukaryotes use mitosis/meiosis.

Interphase

Cell grows, replicates DNA, and prepares to divide.

Prophase

Chromosomes condense, spindle forms, and the nuclear membrane dissolves.

Metaphase

Chromosomes line up in the middle of the cell.

Anaphase

Sister chromatids are pulled apart to opposite poles.

Telophase

New nuclear membranes form and chromosomes uncoil.

Mitosis Phases in Order

Prophase, Metaphase, Anaphase, Telophase.

Meiosis Phases in Order

Meiosis I and Meiosis II, each with Prophase, Metaphase, Anaphase, and Telophase.

Mitosis vs Meiosis

Mitosis makes two identical diploid cells; meiosis makes four unique haploid cells.

Male vs Female Meiosis

Males produce four sperm; females produce one egg and three polar bodies.

Purpose of Mitosis

Growth, repair, and asexual reproduction.

Purpose of Meiosis

Produces gametes for sexual reproduction.

Asexual vs Sexual Reproduction

Asexual involves one parent and identical offspring; sexual involves two parents and genetic variation.

Human Chromosome Number

46 chromosomes (23 pairs).

Chromosomes in Gametes

23 chromosomes in human sperm or egg.

Plant vs Animal Mitosis

Plant cells form a cell plate; animal cells form a cleavage furrow.

Mitosis Products vs Original Cell

Two identical cells with the same DNA as the original.

Meiosis Products vs Original Cell

Four unique cells with half the DNA of the original.

Spindle Function

Moves chromosomes during cell division.

Cytokinesis

Division of the cytoplasm to form two separate cells.

Dominant

Allele that masks another when present.

Recessive

Allele expressed only when the dominant allele is absent.

Homozygous

Having two identical alleles for a trait.

Heterozygous

Having two different alleles for a trait.

Genotype

Genetic makeup of an organism (ex: Aa).

Phenotype

Physical expression of a trait.

Allele

A version of a gene.

Gene

A segment of DNA that codes for a protein.

Pedigree Chart

Diagram showing inheritance of traits through generations.

Karyotype

Picture showing all chromosomes in a cell.

Simple Dominance

One allele completely masks another.

Incomplete Dominance

Heterozygous phenotype is a blend (ex: red + white = pink).

Codominance

Both alleles are expressed equally (ex: AB blood type).

Sex

Linked Traits - Traits carried on the X or Y chromosome.

Blood Type Inheritance

Controlled by multiple alleles (A, B, O).

Male Sex Chromosomes

XY.

Female Sex Chromosomes

XX.

Multiple Alleles

More than two possible alleles for a gene (ex: blood type).

Environmental Effects on Phenotype

Factors like temperature, nutrition, and sunlight can influence traits.

Mutation

A change in the DNA sequence.

Deletion

A base is removed from the DNA sequence.

Insertion

An extra base is added into the DNA sequence.

Point Mutation (Substitution)

One base is replaced with another.

Translocation

Part of one chromosome breaks off and attaches to another.

Duplication

A segment of DNA is copied more than once.

When Mutations Occur

During DNA replication or cell division.

When Mutations Are Inherited

Only if they occur in gametes (sperm or egg).

Benefits of Mutations

Can lead to new traits or adaptations.

Disadvantages of Mutations

Can cause diseases or nonfunctional proteins.