*lecture 6- DNA and chromosomes

Chromosome

A structurally organized single piece of coiled DNA containing many different genes, with each gene coding for one protein

Chromatin

Loosely packed DNA wrapped around proteins in the nucleus that can be accessed for transcription

DNA (Deoxyribonucleic Acid)

The molecule that stores genetic information in living organisms and is composed of nucleotides

Gene

A segment of DNA that contains instructions for making a specific protein

Nucleotide

The basic building block of DNA consisting of a deoxyribose sugar, phosphate group, and nitrogenous base

Deoxyribose

A five-carbon sugar found in DNA nucleotides

Phosphate Group

The component of a nucleotide that forms part of the sugar-phosphate backbone of DNA

Nitrogenous Base

A molecule attached to deoxyribose that carries genetic information

Adenine (A)

A purine nitrogenous base that pairs with thymine in DNA

Thymine (T)

A pyrimidine nitrogenous base that pairs with adenine in DNA

Guanine (G)

A purine nitrogenous base that pairs with cytosine in DNA

Cytosine (C)

A pyrimidine nitrogenous base that pairs with guanine in DNA

Purine

A nitrogenous base with a double-ring structure, including adenine and guanine

Pyrimidine

A nitrogenous base with a single-ring structure, including cytosine and thymine

Double Helix

The twisted ladder shape of DNA formed by two complementary strands

Sugar-Phosphate Backbone

The outer structure of DNA made of alternating deoxyribose sugars and phosphate groups

Base Pairing

The specific pairing of nitrogenous bases where adenine pairs with thymine and guanine pairs with cytosine

Hydrogen Bond

A weak bond that holds complementary DNA bases together

Antiparallel

The arrangement of DNA strands running in opposite 5′ to 3′ directions

Genetic Code

The sequence of nucleotides in DNA that stores hereditary information and determines protein structure

Replication

The process by which DNA makes an exact copy of itself before cell division

DNA Helicase

The enzyme that unzips DNA by breaking hydrogen bonds between base pairs during replication

Template Strand

A DNA strand used as a pattern to build a complementary strand during replication

Complementary Strand

A new DNA strand formed according to base-pairing rules

Semiconservative Replication

The process in which each new DNA molecule contains one original strand and one newly synthesized strand

DNA Polymerase

The enzyme that adds nucleotides to a growing DNA strand during replication

Replication Origin

The specific site on DNA where replication begins

Leading Strand

The DNA strand synthesized continuously in the 5′ to 3′ direction toward the replication fork

Lagging Strand

The DNA strand synthesized discontinuously away from the replication fork

Okazaki Fragment

A short segment of DNA synthesized on the lagging strand during replication

Primase

The enzyme that synthesizes short RNA primers needed to start DNA replication

RNA Primer

A short RNA sequence that provides a starting point for DNA polymerase

Telomere

Repeated DNA sequences at chromosome ends that protect genetic information during replication

Telomerase

An enzyme that extends telomeres by adding repeated DNA sequences to chromosome ends

Telomere Shortening

The gradual loss of chromosome end sequences after repeated rounds of replication

Genetic Information

The hereditary instructions encoded in the nucleotide sequence of DNA

Histone

A protein around which DNA wraps to help organize and package genetic material

Nucleosome

A structural unit of chromatin consisting of DNA wrapped around a group of histone proteins

Eukaryotic Chromosome

A highly condensed DNA-protein structure found in eukaryotic cells, especially visible during cell division

Heterochromatin

Tightly packed chromatin that is generally not being transcribed

Euchromatin

Loosely packed chromatin that is accessible for transcription and gene expression

Chromatin Regulation

The control of gene expression through changes in DNA packaging and chromatin structure

Histone Acetylation

The addition of acetyl groups to histones that loosens DNA and promotes transcription

DNA Methylation

The addition of methyl groups to DNA that usually decreases transcription rates

Transcription

The process of copying genetic information from DNA into RNA

RNA (Ribonucleic Acid)

A single-stranded nucleic acid involved in protein synthesis and gene expression

RNA Polymerase II

The enzyme that synthesizes mRNA from a DNA template during transcription

Transcription Factor

A protein that binds DNA and helps regulate transcription

Promoter

A DNA sequence where RNA polymerase and transcription factors bind to begin transcription

TATA Box

A promoter sequence recognized by transcription machinery to initiate transcription

Control Element

A noncoding DNA sequence where transcription factors bind to regulate gene expression

RNA Modification

Changes made to RNA after transcription that prepare it for translation

Intron

A noncoding RNA sequence removed before translation

Exon

A coding RNA sequence that remains after splicing and is translated into protein

Spliceosome

A complex that removes introns and joins exons together during RNA processing

snRNP (Small Nuclear Ribonucleoprotein)

A particle made of proteins and snRNA that helps form spliceosomes

Lariat RNA

The looped intron structure released during RNA splicing

Protein Structure

The specific arrangement of amino acids in a protein determined by genetic information

Primary Protein Structure

The linear sequence of amino acids in a protein encoded by mRNA

Genetic Variation

Differences in nucleotide sequences that contribute to differences among organisms

Nucleotide Sequence

The order of nucleotides in DNA that determines genetic information and protein production.