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Function of DNA

DNA serves as the organism's genetic blueprint, and the information is stored in the sequence of nitrogen bases.

Structure of DNA

DNA has a double helix structure with sugar and phosphate on the sides and nitrogen bases in the center.

Components of a DNA nucleotide

A phosphate group, deoxyribose sugar, and a nitrogen base (A, T, C, or G).

Complementary base pairing

A pairs with T, and C pairs with G using hydrogen bonds.

Types of bonds between nitrogen bases in DNA

Hydrogen bonds.

Location of DNA in eukaryotic cells

In the nucleus.

Location of DNA in prokaryotic cells

In the cytoplasm.

Central dogma of molecular biology

DNA → RNA → Protein.

Relationship between genes and proteins

Genes code for proteins through transcription and translation.

Transcription

DNA is copied into mRNA by RNA polymerase.

Role of RNA polymerase

It binds to DNA and builds the mRNA strand during transcription.

Function of mRNA

It carries the genetic message from DNA to the ribosome.

Function of tRNA

It brings the correct amino acid to the ribosome during translation.

Function of rRNA

It makes up the ribosome and helps assemble proteins.

Purpose of RNA splicing, the 5' cap, and the poly-A tail

To protect and prepare mRNA for translation.

Translation

The mRNA is read by a ribosome and translated into an amino acid sequence (a protein).

Transcribing DNA to mRNA

Replace A with U, T with A, C with G, and G with C.

Translating mRNA to amino acids

Use a codon chart to convert each mRNA triplet to an amino acid.

Mutation

A change in the DNA sequence.

Types of mutations

Nonsense: creates a stop codon; Missense: changes one amino acid; Silent: does not change the amino acid.

Purpose of mitosis

Growth and repair; produces two identical diploid cells.

Purpose of meiosis

Produces gametes for reproduction; results in four non-identical haploid cells.

Phases of mitosis

Prophase, Metaphase, Anaphase, Telophase, Cytokinesis.

Divisions in mitosis vs. meiosis

Mitosis: 1, Meiosis: 2.

Difference between mitosis in plants and animals

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

Meiosis I vs meiosis II

Meiosis I separates homologous chromosomes; Meiosis II separates sister chromatids.

Difference between haploid and diploid

Haploid has one set of chromosomes (n), diploid has two (2n).

Crossing over

Exchange of genetic material between homologous chromosomes; increases genetic diversity.

Independent assortment

Random distribution of chromosomes into gametes.

DNA replication

During interphase, before mitosis or meiosis starts.

zygote

A fertilized egg.

homologous chromosomes

Chromosomes with the same genes, one from each parent.

tetrad

A pair of homologous chromosomes aligned together during meiosis I.

inheritance (Mendel's conclusion)

Traits are inherited through discrete units (genes), one from each parent.

principle of dominance

Some alleles are dominant, others recessive; dominant alleles mask recessive ones.

genotype

The genetic makeup of an organism (e.g., Bb, TT).

phenotype

The physical expression of a trait (e.g., tall, blue eyes).

homozygous

Having two of the same alleles (BB or bb).

heterozygous

Having two different alleles (Bb).

Punnett square

To predict the probability of offspring genotypes and phenotypes.

test cross

Crossing an organism with a dominant phenotype with a homozygous recessive to determine genotype.

monohybrid vs dihybrid cross

Monohybrid: 1 trait, Dihybrid: 2 traits.

pedigree

A family tree that shows how a trait is inherited across generations.

autosomal vs sex-linked traits

Autosomal are on non-sex chromosomes; sex-linked are on X or Y chromosomes.

Darwin's theory of natural selection

Organisms with beneficial traits survive and reproduce more successfully.

homologous structures

Similar structures with different functions—support common ancestry (e.g., whale fin, human arm).

analogous structures

Different structures with similar functions—do not support common ancestry (e.g., bird wing, insect wing).

vestigial structures

Structures with no current function that suggest evolutionary history (e.g., human appendix).

embryology and evolution

Similar embryos suggest common ancestry.

amino acid sequences

More similarities = more closely related.

heritable variation in evolution

It provides the raw material for natural selection to act on.

Hardy-Weinberg principle

It describes a non-evolving population; used to track allele frequencies.

group behavior

Behaviors like flocking or herding increase survival and reproduction.

carrying capacity

The maximum number of individuals an environment can support.

limited resources in an ecosystem

Organisms compete; traits that improve survival are selected for.

food web

A diagram that shows the flow of energy and matter through organisms.

trophic levels

Levels in a food chain: producers → primary → secondary → tertiary consumers.

energy in food chain

It decreases—only about 10% is transferred to the next level.