Biology Chapter 25 Exam

DNA molecule

consists of two strands of nucleotide monomers running in opposite  directions and coiled into a double helix

DNA nucleotide

1. A 5 carbon sugar (deoxyribose)

2. 3 phosphate groups

3. One nitrogen-containing base (adenine, thymine, guanine, or cytosine)

DNA is described as a

“double-helix”

Phosphate sugar backbone

on outside

 Paired bases on inside – complementary base pairing

Adenine to Thymine (A&T); Guanine to Cytosine (G&C)

DNA structure is held together by?

Hydrogen Bonds

Condensed (DNA)

A eukaryotic chromosome is a molecule of DNA together with associated proteins

Chromosome

 Structure made of condensed DNA (and associated proteins)

 1. Carries part or all of a cell’s genetic information

A eukaryotic cell’s DNA is divided into a characteristic number of?

Chromosomes

Chromosome Number

Sum of all chromosomes in a cell of a given type

A human body cell has ___ pairs of chromosomes or ____ total chromosomes

23 and 46

Diploid

Body or somatic cells in humans have 23 pairs or 46 total chromosomes

1. Cells having two of each type of chromosome characteristic of the species (2n)

Haploid

 Gametes or sex cells in humans have 23 total chromosomes

1.  Cells having one type of chromosome characteristics of species (1n)

There are two types of eukaryotic chromosomes:

autosomes and sex chromosomes

Autosomes

Paired chromosomes with the same length, shape, centromere location, and genes

Sex chromosomes

Members of a pair of chromosomes that differ between males and females

A cell replicates its DNA before it ____?

Divides

Each strand of the double helix serves as a template for synthesis of a new?

complementary strand of DNA.

1. One old strand makes two new strands

DNA enzymes use each strand as a template to assemble new, complementary strands of DNA from free nucleotides?

DNA enzymes seal any gaps in the new strands

DNA replication results in?

two double-stranded DNA molecules identical to the parent

Semiconservative =

2 DNA helices of 1 old strand & 1 new strand

DNA helicase

unzips DNA @ weak Hydrogen bonds between bases

New DNA nucleotides replace old ones & join by?

DNA polymerase

DNA ligase

seals any breaks in backbone

2 new helices are identical to each other & original

each has 1 old & 1 new strand

 DNA repair mechanisms

 Any of several processes by which enzymes repair DNA damage

DNA repair mechanisms?

fix damaged DNA

Differentiation

The process by which cells become specialized

Genes

segments of  DNA found on chromosomes that specify the aa sequence of proteins

DNA sequence

The information it carries in found in the pattern of nucleotides

Gene Expression

 RNA assists DNA in directing the cell’s activities and determining the cell’s specialty

Eukaryotic genes may encode?

 “housekeeping genes”

Transcription

DNA is transcribed letter by letter into RNA

Translation

RNA directs the production of proteins controlling structure & process of cells

mRNA

takes message from DNA in nucleus to ribosomes in cytoplasm (contractor)

rRNA

makes up ribosomes where proteins are made (carpenter or construction worker)

tRNA

transfers amino acids to ribosomes (supplier)

WHAT IS RNA?

 1. Polynucleotide

2. Contains ribose sugar

 3. Adenine To Uracil (instead of thymine), Guanine to Cytosine

4. Single-stranded

Transcription is the process of reading?

protein blueprint

A gene’s nucleotide base sequence encodes instructions for ______?

building an RNA or protein product

Translation, the second part of protein synthesis, occurs in the?

cytoplasm

Translation  converts the protein-building information carried by an mRNA into a

polypeptide

Ribosomal RNA, rRNA reads the messenger RNA, mRNA and acts as an enzyme to form peptide bonds between amino acids,  assembling them into a?

polypeptide chain

Codon

In mRNA, a nucleotide base triplet that codes for an amino acid or stop signal in translation

1. Codons  constitute the genetic code

Translation has 3 stages?

1. Initiation

2. Elongation

3. Termination

Initiation

mRNA joins with tRNA and ribosome

Elongation

tRNA delivers amino acids to ribosome in the order indicated by the mRNA codons

Termination

Stop codon signals end of polypeptide

Anticodon

 Set of three nucleotides in a tRNA

Mutations

permanent changes in the nucleotide sequence of DNA, which may alter a gene product and lead to malfunctioning proteins and cells

A mutation that changes a gene’s product may have

harmful effects

Errors in DNA replication

typically only 1 mistake every 1 billion nucleotide pairs replicated

Mutagens

environmental influences that cause mutations in humans (radiation, Xray, UV rays, cigarette smoke)

Ionizing radiation (x-rays)

 breaks chromosomes and produces free radicals

Deletion

 Mutation in which one or more base pairs are lost

Insertion

 Mutation in which one or more base pairs become inserted into DNA

Base-pair substitution

substituting one nucleotide for another

1.  Causes Sickle-cell anemia

Dosage compensation

Theory that X chromosome inactivation equalizes gene expression between males and females

SRY gene

found on the Y chromosome, is the master gene for male sex determination

tumor suppressors

Checkpoint genes whose products inhibit meiosis are called

cancer

Failure of cell cycle checkpoints results in the uncontrolled cell divisions that characterize

Mutations of the BRCA gene

found in breast and ovarian cancer cells

Tumor

◦Abnormally growing and dividing mass of cells

Moles and other tumors are

benign and noncancerous

Malignant tumor (cancerous)

occurs when abnormally dividing cells disrupt body tissues, physically and metabolically

genetic engineering

 Alternation of genomes for medical & industrial purposes

Reproductive cloning

technology that produces genetically identical individuals- making baby

Therapeutic cloning

 using SCNT to produce human embryos for research; use stem cells from the cloned human embryos

 Somatic cell nuclear transfer (SCNT)

 Method of reproductive cloning in which researchers remove the nucleus from an unfertilized egg, then inserts into the egg the nucleus from an adult animal cell

PCR

used to copy a region of a chromosome

Electrophoresis

Used to separate DNA fragments by size

1. Pulls DNA fragments through gel

Human Genome

An organism’s complete set of genetic material

1. Sequenced in 2001 (the order of nucleotide bases)

Genomics

The study of genomes (structural genomics, comparative genomics)

Eugenics

Idea of deliberately improving the genetic qualities of the human race