Chapter 4 - Genes and Cellular Function

how many rings are purines?

double ring

how many rings are pyrimidines?

single ring

what are the nitrogenous base(s) for purines?

Adenine (A)

Guanine (G)

what are the nitrogenous base(s) for pyrimidines?

Cytosine (C)

Thymine (T)

Uracil (U) - replaces T in RNA

three things that make up a nucleotide:

one sugar (deoxyribose)

one phosphate group

one nitrogenous base (purines / pyrimidines)

how is DNA paired

A purine on one strand bound to a pyrimidine on the other.

what does adenine (A) bind to?

**vice versa

thymine (T)

what does cytosine (C) bind to?

**vice versa

guanine (G)

how many hydrogen bonds in A-T?

two hydrogen bonds

how many hydrogen bonds in C-G?

three hydrogen bonds

gene

segment of DNA coding for the synthesis of a specific protein

genome

all the genes of one person

• humans have about 20,000 genes

chromatin

one long DNA molecule and its associated proteins

nucleosome

strand of DNA coiled around the group of histone proteins

histone

proteins crucial for DNA packing

kinetochores

protein plaques on each side of centromere

what is the orange thing in the middle?

kinetochore

transcription

copying genetic instructions from DNA to mRNAel

Messenger RNA

mRNA

• carried code from nucleus to cytoplasm

• protein cap that is recognition site for ribosome

Transfer RNA

tRNA

• delivers a single amino acid to the ribosome

• contains an anticodon

anticodon

series of 3 nucleotides that are complementary to the mRNA codon

translation

occurs at ribosome. sequence of mRNA is translated into amino acid sequence with help of tRNA

gene regulation

genes can be turned on and off

example of gene regulation?

mammary gland cells turn on gene for casein protein ONLY when breast milk is produced

stages of interphase

G1, S, G2

G1 - first gap phase

interval between cell birth and DNA replication

• cell is normal and accumulates materials for next phase

S - synthesis phase

cell replicates all nuclear DNA and duplicates centrioles

G2 - second gap phase

interval between DNA replication and cell division

• cell repairs DNA replication errors, grows and synthesizes enzymes for cell division

G Zero Phase

cells that have left the cycle and cease dividing for a long time (sometimes permanently)

heredity

transmission of genetic characteristics from parent to offspring

karyotype

chart of 46 chromosomes laid out in order by size

homologous chromosomes

1 chromosome from each pair is inherited from each parent

• 22 pairs autosomes

• 1 pair of sex chromosomes

female sex chromosomes

homologous pair of X chromosomes

XX

male sex chromosomes

one X and one much smaller Y

XY

tumor angiogenesis

growth of blood vessels due to energy hungry tumors

carcinoma

cancer in epithelial tissue

lymphoma

cancer in lymph nodes

melanomas

cancer in pigment cells of epidermis (melanocytes)

leukemia

cancer in blood forming tissues

sarcomas

cancer in bone, other connective tissue, or muscle

polygenic inheritance

genes at 2 or more loci contribute to ONE phenotype

pleiotropy

one gene produces multiple phenotypic effectse

epigenetic effects

mechanisms that alter the gene expression W/O changing the DNA base sequence

sugar in DNA/RNA

deoxyribose / ribose

site of action of DNA/RNA

nucleus / leaves nucleus → cytoplasm

function of DNA/RNA

synthesis of RNA and proteins / carries out instructions for DNA, assembles proteins

Transcription initiation

Protein transcription factor binds to promotor region near gene on template strand

Transcription elongation

RNA polymerase covalently bonds complementary RNA nucleotides to growing mRNA molecules

Transcription termination

Last triplet of gene is reached and the newly pre-mRNA molecule is ready for modification

Translation initiation

Initiator tRNA bind to mRNA start codon (Met) on the ribosome

Translation elongation

Next tRNA binds to open site allowing two amino acids to be covalently linked by a peptide

Translation termination

End of translation, occurs when ribosome reaches stop codon on mRNA (UAA, UGA, UAG)

Stop codons (3)

UAA (u are away)

UGA (u go away)

UAG (u are gone)