DNA, Genetics, and Cell Division Study Guide

DNA

Deoxyribonucleic acid, carries genetic information.

Nucleotide

The building block of DNA, made of a sugar, phosphate group, and nitrogen base.

Pentose sugars

5-carbon sugars: deoxyribose (in DNA), ribose (in RNA).

Nitrogen bases

Adenine, Thymine, Cytosine, Guanine (Uracil in RNA).

Complementary base pairing

A pairs with T (or U in RNA), G pairs with C.

Double helix

Shape of the DNA molecule.

Sugar-phosphate backbone

Holds DNA strands together.

Hydrogen bonds

Weak bonds between nitrogen bases.

Covalent bonds

Strong bonds in the sugar-phosphate backbone.

DNA replication

Copying DNA before cell division.

Transcription

Making RNA from DNA.

Translation

Making proteins from RNA.

PCR (Polymerase Chain Reaction)

Technique to amplify DNA.

Gene mutation

A change in DNA sequence.

Gene expression

How a gene produces its product (protein).

Rosalind Franklin, Maurice Wilkins, Watson & Crick

Scientists who contributed to discovering DNA's structure.

DNA subunits

Nucleotides (composed of a sugar-phosphate backbone with one nitrogen base).

Base pairing rule

A-T, G-C.

DNA vs RNA

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

DNA's functions

Stores genetic info, replicates, guides protein synthesis.

Gene mutations

Can change amino acid sequences, potentially altering protein structure and function.

Chromosome

DNA and protein structures that carry genes.

Chromatid

One half of a duplicated chromosome.

Centromere

Region connecting two chromatids.

Autosomes

Non-sex chromosomes (22 pairs in humans).

Sex chromosomes

X and Y chromosomes; determine biological sex (1 pair in humans).

Karyotyping

Visualising chromosomes to detect disorders.

Chromosomal disorder

Abnormal number/structure of chromosomes.

Trisomy

Three copies of a chromosome (e.g., Down syndrome = trisomy 21).

Monosomy

One copy of a chromosome (e.g., Turner syndrome = monosomy X).

Mitosis

Cell division producing identical cells for growth and repair.

Meiosis

Cell division producing gametes (sperm/egg) with half the chromosome number.

Parent cell

Original cell before division.

Daughter cell

Resulting cells after division.

Gamete

Sex cell (sperm or egg), haploid.

Haploid

Half the number of chromosomes (23 in humans).

Diploid

Full set of chromosomes (46 in humans).

Fertilisation

Union of sperm and egg to form a zygote.

Zygote

First cell of a new organism after fertilisation.

Prophase, Metaphase, Anaphase, Telophase, Cytokinesis

Stages of cell division in both mitosis and meiosis.

Mitosis produces

2 identical daughter cells; meiosis produces 4 genetically different daughter cells.

Mitosis: daughter cells

have 46 chromosomes; Meiosis: daughter cells have 23 chromosomes.

Mitosis is used for

growth and repair; meiosis is used for reproduction.

DNA

DNA = deoxyribonucleic acid, lives in the nucleus.

Genetic Blueprint

Instructions for how each cell behaves.

Proteins

Substances that give us our specific characteristics.

Genes

Sections of DNA that contain instructions to produce specific proteins.

Chromatin

A very long (3m) strand of DNA that can't be seen under a light microscope.

Chromosomes

Condensed, shortened, and thickened form of chromatin visible during cell division.

Humans Chromosomes

Humans have 46 chromosomes in 23 pairs, with one of each pair from each parent.

Autosomes

22 pairs of chromosomes that are numbered from 1 to 22 based on size.

Homologous pairs

Chromosomes from each parent that are identical in terms of size, shape, and type of genes they carry.

Karyotyping

A technique that allows us to look at chromosomes in utero and check for abnormalities.

Gametes

Sperm and ova that each have 23 chromosomes, allowing them to combine to make a full set.

Non-disjunction

A failure in meiosis where chromosomes do not separate properly, leading to gametes with too many or too few chromosomes.

Chromosomal mutation

A genetic alteration that occurs if gametes with abnormal chromosome numbers end up in the zygote.

Down syndrome

A chromosomal abnormality caused by having 3 copies of chromosome 21, characterized by distinct facial appearance and intellectual disability.

Turner's syndrome

A condition in females caused by missing an X chromosome, characterized by short stature and infertility.

Klinefelter's syndrome

A condition in males caused by an extra X chromosome, leading to characteristics such as delayed puberty and infertility.

Jacobs syndrome

A condition in males caused by an extra Y chromosome, characterized by tall stature and behavioral issues.

DNA monomers

Nucleotides, which are the repeating subunits of DNA.

DNA

A polymer made up of monomers called nucleotides.

Nucleotides

The building blocks of DNA, consisting of a nitrogenous base, a deoxyribose sugar, and a phosphate group.

Nitrogenous bases

The four different components of nucleotides: Adenine (A), Guanine (G), Cytosine (C), and Thymine (T).

Purines

Nitrogenous bases with two rings, specifically Adenine (A) and Guanine (G).

Pyrimidines

Nitrogenous bases with one ring, specifically Cytosine (C) and Thymine (T).

Protein synthesis

The process by which DNA tells the cell how to make proteins.

Transcription

The process of making a copy of DNA (template strand) and taking it into the cytoplasm via messenger RNA (mRNA).

Messenger RNA (mRNA)

The single-stranded copy of DNA that carries the genetic information to the cytoplasm.

Uracil

A nitrogenous base that replaces Thymine in RNA.

Covalent bonds

The type of bonds that join the phosphate group and deoxyribose sugar in nucleotides.

Hydrogen bonds

The type of bonds that join the nitrogenous bases in DNA.

Anti-parallel strands

The orientation of the two strands of DNA running in opposite directions.

Ribose

A sugar that is not deoxyribose.

RNA polymerase

An enzyme that unzips DNA by breaking hydrogen bonds and connects an RNA strand to one of the DNA strands.

Transcription

The process that begins when RNA polymerase unzips the section of DNA corresponding to the gene for a particular protein.

mRNA

Messenger RNA that adds free nucleotides to the exposed strand according to base pairing rules.

Codon

A sequence of three bases on the mRNA strand that represents an amino acid.

Amino acids

The building blocks of proteins.

Stop codons

Three codons (UAA, UAG, UGA) that indicate the end of the gene.

tRNA

Transfer RNA that carries the amino acid corresponding to the mRNA codon to the ribosome.

Anti-codon

A three-base sequence on tRNA that binds with the mRNA codon.

Peptide bond

A strong bond formed when two amino acids are brought together.

Polypeptides

Long chains of amino acids.

Protein functions

Important purposes include providing structure, regulating body processes, transporting materials, helping with immunity, and providing energy.

DNA replication

The process of creating new DNA strands using existing strands as templates.

Helicase

An enzyme that unwinds and separates the two strands of DNA by breaking hydrogen bonds.

DNA polymerase

Enzymes that attach to exposed strands and synthesize new strands of DNA.

Semi-conservative replication

A process where each of the two created DNA molecules contains one original strand and one newly synthesized strand.

Gene regulation

The process by which RNA polymerase copies only the wanted genes.

Stem cells

Unprogrammed cells that can differentiate into various cell types.

Epigenetics

An emerging field suggesting that life experiences can affect gene expression in offspring.

Nucleus

The cell organelle where DNA is stored and transcription occurs.

Cytoplasm

The part of the cell where tRNA retrieves amino acids.

25000 genes

The approximate number of genes present in every cell.

Locus

Position of gene on its specific chromosomes.

Linked genes

Genes on the same chromosome.

Cell division

The process by which cells grow, repair damaged tissue, or prepare for sexual reproduction.

Mitosis

Type of cell division for growth and repair.

Meiosis

Type of cell division for the production of gametes.