Chapter 4: Genetic Control Flashcards
Genetics
study of the mechanism of heredity and variations in inherited traits
Genomics
study of the function of all the nucleotide sequences (entire genomes of human beings)
Genes
specific set of instructions that cells use to produce a specific protein – tells a cell what it will be, how it will function, what traits are going to be expressed
Human Genome
all of the DNA that a human being possesses – complete set of genes
humans have approximately 20,000 genes in the body (can vary slightly)
Human Genome (2)
- 9% of these sequences are almost exactly the same in everyone
- 01% accounts for individual differences (physical appearance, behaviors, disease susceptibility)
Gene regulators
turn genes “on” and “off” in different cells to maintain control
Germ cells/Gametes
sperm and ovum – only contain half set of chromosomes
Haploid
set of 23 chromosomes
example: sperm, ovum
Diploid
full set of 46 chromosomes
example: zygote
Chromosomes
entire chain of DNA, folded in specific way (if not, mutation occur)
Histones
protein that provides structural support for chromosomes, DNA is tightly coiled around
control exact folding of the DNA strand
Locus
specific location of a gene on a chromosome
used to name certain genes
Pharmacogenetics
genes that metabolize drugs either more quickly or slowly - drugs developed specifically with these genes in mind
5 Functions of Genes
directs function of body cells determines appearance dictates how we respond to the environment serves as the unit of inheritance determines our disease susceptibility
DNA Nitrogenous Bases
adenine and thymine
guanine and cytosine
DNA Helicases
enzyme that separates the two strands, duplicating genetic information and creating the double helix
Chromatin
tightly coiled structure that contain DNA molecules, proteins, and small amount of RNA
Accidental Errors in Replication
DNA Mutations
substitution of 1 base pair for another
loss/addition of > 1 base pair
rearrangement of base pairs
causes: spontaneous, environmental, chemicals/radiation
Polymorphisms
normal variations in DNA replication
don’t cause problems - body can repair mutations in DNA if caught in time
RNA
assembles the amino acids into functional protein during the translation process
differences from DNA: single-stranded, sugar is ribose, and thymine is replaced by uracil
Messenger RNA
carries instructions for protein synthesis in sequence of 3 bases (codon)
61 triplets make up a specific amino acid
3 triplets are stop codons to end a protein molecule
Ribosomal RNA
interprets the instructions
produces ribosomes
connects amino acids that tRNA have carried into position
Transfer RNA
reads the instructions
carries a specific amino acid to the protein being made in the ribosomes and lines up, matching its anticodon to mRNA’s codon
Transcription
occurs in the cell nucleus
process where RNA is synthesized from the DNA template (initiated by RNA polymerase)
Translation
occurs in the cytoplasm
mRNA acts as a pattern telling the cell how to line up amino acids to form a protein
tRNA delivers and transfers amino acids into proper positions on the peptide chain
polypeptide chain is released when the termination (stop) codon is read
Molecular Chaperones
helps fold up new polypeptide chains (from translation) into its unique 3D conformation and transports it to the cell where it will perform its functions
Gene expression
the degree to which a gene or group of genes are actively being transcribed
Induction
gene expression is increased
Repression
regulatory gene that reduces or prevents gene expression
Transcription factors
regulate gene transcription through a negative feedback loop
occurs when levels are too low (induction) or too high (repression)
Cytogenetics
study of the structure and numeric characteristics of the cell’s chromosomes
can be done on any tissue or cell that grows and divides in culture
colchicine is used to arrest mitosis in metaphase to be easily observed
Karyotype
photographic arrangement of chromosomes
Chromosome Structure
takes the form of an X or wishbone pattern
P arm - short arm
Q arm - long arm
Telomere
protects the chromosome during division
each time the cell goes through division, the telomere shortens
when the telomere is gone, cell can no longer divide
Telomerase
produced by cancer cells to continue the production of telomeres = unregulated, infinite cell division
Metacentric
centromere located in the middle
arms are similar lengths
Submetacentric
centromere is not centered
arms are clearly different lengths
Acrocentric
centromeres located at/very near polar ends
Mitosis
DNA replication to produce somatic cells
each new cell has an identical set of 23 pairs of chromosomes (46 chromosomes total)
occurs in a regular pattern (cell cycle)
Meiosis
DNA replication to produce germ cells (gametes)
one single set of 23 chromosomes
G0 Phase
cell cycle
cells are resting
cancer cells very rarely enter the G0 phase
G1 Phase (cell cycle - interphase)
growing phase - cells increase in size, produce RNA and protein
CHECKPOINT to ensure everything is ready for DNA synthesis
recedes S phase
S phase (cell cycle - interphase)
synthesis - DNA replication
G2 Phase (cell cycle - interphase)
cell continues to grow and produce new proteins
CHECKPOINT to determine if cell can enter mitosis and divide
precedes M phase
M Phase
cell cycle - mitosis
cell division
involves prophase, metaphase, anaphase, telophase
Interphase
phase of the cell cycle before division where mass and content of the cell is doubled
G0, G1, S phase, G2
Gametogenesis
diploid cells to haploid cells through meiosis
results in 4 haploid cells capable of producing offspring
Spermatogenesis
head houses the nucleus and DNA
tail promotes motility
begins at puberty and continues through life
Oogenesis
meiosis 1 - one ova and one polar body
meiosis 2 - 2 separate ova
starts prior to birth
Fertilization
union of mature haploid sperm with mature haploid ovum = diploid zygote
Genotype
an exact gene allele composition that a person has for a single gene trait`
Phenotype
the observed expression of a specific gene
Allele
alternative form/variation of a specific location of each gene on a chromosome
Genomic imprinting
process by which only one copy of a gene in an individual (from their mother or father) is expressed, while the other copy is suppressed
examples: Angelman and Prader-Willi syndrome (chromosome 15)
Angelman Syndrome
receive defective chromosome 15 from mother
mental retardation, aphasia, gait imbalances
Prader-Willi Syndrome
receive defective chromosome 15 from father
mild to moderate MR, short stature, obesity
Single Gene Disorders (Mendel Laws)
results from a mutation that caused the protein product of a gene to be altered or missing
autosomal dominant disorders
autosomal recessive disorders
X-linked inheritance
Autosomal Dominant Inheritance
male and female offspring are affected equally
if one parent is affected = 50% chance children are affected
if both parents are affected = 100% change children are affected
no carrier status
Autosomal Recessive Inheritance
must by homozygous for a trait to express it
if both parents are unaffected but heterozygous for trait (carriers) = 25% chance of children being affected
if one parent is affected and the other a carrier, children have 50% chance of being affected
X-Linked Inheritance
single gene disorders that are passed through the X chromosome
If father has defective X gene, males will be unaffected (gets Y) but all daughters will be carriers or affected (50/50)
If mother contributes X chromosome to male = affected
Carrier
individual that carries the defective gene but does not express it (phenotypically normal)
can transfer to their offspring who can become affected
Chromosomal Disorders
caused by chromosomal aberrations - deviation in either the structure or number of chromosomes
Disjunction
normal separation during cell division
Nondisjunction
failure to separate during cell division
can lead to unequal distribution of chromosomes between cells
Aneuploidy
abnormal number of chromsomes
Trisomy
extra chromosome (3 instead of pair of 2)
Monosomy
only one chromosome (loss of a chromosome)
Polyploidy
abnormal number of the entire haploid chromosome set
triploidy = 3x the number in nucleus
tetraploidy = 4x the number
Deletion
loss of a portion of a chromosome
Duplication
presence of a repeated gene or gene sequence
Inversion
reversal of gene order
linear arrangement of genes breaks off and the order gets reversed when it reattaches
Translocation
abnormal arrangement of part of a chromosome
Recombinant DNA Technology
combination of DNA molecules not found together in nature
Examples: pharmaceuticals (insulin, human GH, erythropoietin)
DNA fingerprinting
Gene therapy
