Chapters 8-10 Flashcards
Cell division
Reproduction. Produces two “daughter” cells that are genetically identical to each other and to the original “parent” cell.
Chromosomes
Structures that contain most of the cell’s genetic information in the form of DNA.
Asexual reporduction
Creation of genetically identical offspring by a single parent. Gives rise to a clone.
Clone
A group of genetically identical individuals.
Sexual reporduction
Requires the fusion of gametes.
Zygote
Fertilized egg.
Binary fission
“Dividing in half.”
Stages of a binary fission in a prokaryote
- As chromosome is duplicating, one copy moves toward the opposite end of the cell.
- Cell elongates
- Duplication is complete; plasma membrane pinches inward, which forms a cell wall, which divides parent cell into two daughter cells.
Cell cycle
Ordered sequence of events that run from the instant a cell is first formed from a dividing parent cell until its own division into two cells.
2 main stages of cell cycle
- interphase: growing phase. Cell doubles in its cytoplasm and replicates its DNA
- mitotic phase: actual cell division
interphase
Period of cell growth when cell synthesizes new molecules and organelles.
- G(1) phase: “first gap”
- S phase: “synthesis” of DNA - aka DNA replication
- G(2) phase: “second gap”
Mitosis phases
Prophase, prometaphase, metaphase, anaphase, and telophase
Prophase
Chromatin fibers in nucleus become more tightly coiled and folded, forming discrete chromosomes.
Metaphase
Mitotic spindle is fully formed. Chromosomes line up on metaphase plate.
Anaphase
Chromosomes separate and move towards the poles
Telophase
Cell elongation continues. Forms a cleavage furrow, then splits.
Cytokinesis
Division of cytoplasm and usually occurs simultaneously with telophase.
Anchorage
When cells must be in contact with a solid surface to divide.
Cell cycle control system
Set of molecules that both triggers and coordinates key events in the cell cycle.
Tumor
A mass of abnormally growing cells within otherwise normal tissue.
Benign tumor
Tumor where abnormal cells remain at their original site.
Malignant tumor
Mass of abnormally reproducing cells that can spread into neighboring tissues and invade other parts of the body. A individual with this type of tumor is said to have cancer.
Metastasis
The spread of cancer cells beyond their original site.
Somatic cell
A typical body cell in humans. Usually has 46 chromosomes. Changes in these cells do not influence gametes.
Homologous chromosomes
The two chromosomes that are twins of each other. Every diploid cell has pairs of these.
Autosomes
Chromosomes other than sex hormones.
Life cycle
Sequence of generation-to-generation stages in the history of an organism.
Gametes
Egg and sperm cells. Only cells of the human body that are not produced by mitosis.
Haploid cell
Cell with a single chromosome set.
Meiosis
Type of cell division that produces haploid gametes in diploid organisms. Has to consecutive cell divisions: mieosis I and meiosis II
meiosis phase
Meiosis I separates the members of each homologous pair and produces two daughter cells, each with one set of chromosomes.
Meiosis II is essentially the same as mitosis:
-In each of the cells, the sister chromatids of each chromosome separate.
The result is a total of four haploid cells.
Crossing over
Exchange of corresponding segments between nonsister chromatids of homologous chromosomes.
Recombinant chromosomes
Result of crossing over. Chromosomes that carry DNA from two different parents.
Nondisjunction
In which members of a chromosome pair fail to separate.
Karyotype
Ordered display of magnified images of an individual’s chromosomes arranged in pairs.
Trisomy 21
when there are three number 21 chromosomes, which results in 47 chromosomes in total.
Deletion
Occurs when a chromosomal fragment (with its genes) becomes detached.
In typical prokaryotes, most genes are carried on…
one circular DNA molecule that, with associated proteins, constitutes the organism’s chromosome.
Heredity
Transmission of traits from one generation to the next.
Genetics
Scientific study of heredity.
Character
A heritable feature that varies among individuals
Trait
Each variant for a character
True-breeding
Where self-fertilization produces offspring all identical to the parent.
Hybrds
Offspring of two different varieties
Cross
Hybridization. Cross-fertilization itself
P generation
True-breeding parents
F(1) generation
Hybrid offspring of P generation
F(2) generation
When F(1) plants self-fertilize or fertilize each other
Alleles
Alternative versions of a gene
Homozygous
When an organism that has two identical alleles for a gene
Heterozygous
When an organism that has two different alleles for a gene.
Dominant allele
When two alleles of an inherited pair differ, the dominant allele determines the organism’s appearance
Recessive allele
Is the allele that has no noticeable effect on the organism’s appearance when two alleles of an inherited pair differ.
Law of segregation
A sperm or egg carries only one allele for each inherited character because allele pairs separate (segregate) from each other during the production of gametes.
Locus
A specific location of a gene along the chromosome
Dihybrid
Cross between two organisms that are each heterozygous for two characters being followed.
Law of independent assortment
The inheritance of one character has no effect on the inheritance of another.
-the alleles of a pair segregate independently of other allele pairs during gamete formation.
Testcross
Mating between an individual of an unknown genotype and a homozygous recessive individual
Rule of multiplication
1/2 * 1/2 = 1/4
-probability of two independent events occurring.
Rule of addition
1/4 + 1/4 = 1/2
-Probability of an event that can occur in alternative ways.
Complete dominance
When the dominant allele has the same phenotypic effect whether present in one or two copies.
Incomplete dominance
Appearance of F(1) hybrids falls between the phenotypes of the two parental varieties.
ABO blood group
Phenotype in humans that is controlled by three alleles that produce a total of four phenotypes.
Codominant
Both alleles are expressed in heterozygous individuals
Pleiotropy
One gene influences multiple characters. ex: sickle-cell disease
Polygenic inheritance
a single phenotypic character results from the additive effects of two or more genes on a single phenotypic character.
Chromosome theory of inheritance
- Genes occupy specific loci (positions) on chromosomes, and
- chromosomes undergo segregation and independent assortment during meiosis.
Linked genes
Genes located close together on the same chromosome tend to be inherited together.
Wild-type
Traits most common in nature
Mutant
Traits less common in nature.
Recombination frequency
The percentage of recombinant offspring among the total
Genetic map
An ordered list of the genetic loci along a chromosome
Sex-linked gene
Gene located on either sex chromosome. Majority are X-linked genes.
Punnett square
shows the four possible combinations of alleles that could occur when these gametes combine.
monohybrid cross.
A cross between two individuals that are heterozygous for one character
dihybrid cross
is a mating of parental varieties that differ in two characters.
heterozygotes
parents who are carriers of the recessive allele for the disorder but are phenotypically normal
Linkage map
a genetic map based on recombinant frequencies
Bacteriophages/phages
viruses that exclusively infect bacteria
nucleotides
what make nucleic acids in RNA and DNA. Made from long chains (polymers) of chemical units (monomers)
polynucleotide
one of the two strains in DNA. a nucleotide polymer (chain)
what does a nucleotide consist of?
three components:
- a nitrogenous base (A,C,T, or G in DNA)
- a five-carbon sugar,
- phosphate group. joined by a sugar-phosphate backbone
two types of bases
single-ring structures called pyrimidines: thymine and cytosine
larger, double-ring structures called purines: adenine, guanine
RNA
ribonucleic acid
- uses sugar ribose rather than deoxyribose
- nitrogenous base uracil
DNA
deoxyribonucleic acid
- uses deoxyribose
- nitrogenous base thymine
double helix
two polynucleotide strands wrapped around each other in DNA
-held together by hydrogen bonds between the bases
C-G base pair
has functional groups that form three hydrogen bonds
A-T base pair
has functional groups that form two hydrogen bonds
primary function of DNA
encode and store genetic information
-act as the basis of heredity
semiconservative model
model that DNA replication follows.
- The two DNA strands separate.
- Each strand then becomes a template for the assembly of a complementary strand from a supply of free nucleotides.
- Each new DNA helix has one old strand with one new strand.
DNA replication starts…
with the separation of DNA strands.
-Enzymes then use each strand as a template to assemble new nucleotides into a complementary strand.
DNA polymerases
enzymes that link DNA nucleotides to a growing daughter strand
-only add nucleotides to 3’ end of the strand
DNA ligase
enzyme that links, or ligates, Okazaki fragments into a single DNA strand
DNA replication
- Using the DNA polymerase, the cell synthesizes one daughter strand as a continuous piece.
- The other strand is synthesized as a series of short pieces, which are then connected by the enzyme DNA ligase.
genotype
An organism’s genetic makeup.
-heritable information contained in the sequence of nucleotide bases in DNA
phenotype
organism’s physical/observable traits
two main stages of DNA to protein
- transcription: the synthesis of RNA under the direction of DNA
- translation: the synthesis of proteins under the direction of RNA
Flow of information within the cell
DNA => RNA => protein
triplet code
basis of flow information from gene to protein. The genetic instructions for the amino acid sequence of a polypeptide chain are written in DNA and RNA as codons
codons
a series of nonoverlapping three-base “words”
genetic code
set of rules that dictate the amino acid translations of each of the mRNA nucleotide triplets
RNA polymerase
transcription enzyme
promoter
a specific nucleotide sequence that acts as a binding site for RNA polymerase and determines where transcription starts.
terminator
a sequence of DNA bases that signal the end of the gene
messenger RNA (mRNA)
the kind of RNA that encodes amino acid sequences
introns
“intervening sequences.” internal non-coding regions
exons
coding regions - the parts of a gene that are expressed
RNA splicing
- introns (non-coding segments of RNA) are spliced out,
- exons (the parts of a gene that are expressed) are spliced together
- a cap and tail are added to the ends of the mRNA.
transfer RNA (tRNA)
transfer amino acids from the cytoplasmic pool to a growing polypeptide in a ribosome.
- must pick up appropriate amino acids
- recognize the appropriate codons in mRNA
anticodon
Each tRNA is a folded molecule bearing a base triplet on one end
where does translation take place?
cytoplasm
ribosomes
structures in cytoplasm that coordinate the functioning of mRNA and tRNA and catalyze the synthesis of polypeptides.
- made of ribosomal RNA (rRNA) and proteins
- have binding sites for tRNAs and mRNA.
translation phases
initiation, elongation, termination
start codon
a special initiator tRNA base-pairs with specific codon
P side
where initiator tRNA fits into a tRNA binding site on the ribosome
A side
other tRNA binding site
Initiation brings together…
- mRNA,
- a tRNA bearing the first amino acid, and
- the two subunits of a ribosome.
mutation
any change to genetic information of a cell or virus
nonsense mutation
change an amino acid codon to a stop codon
mutagens
caused by physical or chemical agents
virus
an infectious particle consisting of little more than “genes in a box”
capsid
protective coat around a virus
lytic cycle
When phage DNA enters a lytic cycle inside a bacterium, it is replicated, transcribed, and translated.
lysogenic cycle
phage DNA inserts into the host chromosome and is passed on to generations of daughter cells.
prophage
what the phage DNA is referred to once inserted
emerging viruses
are ones that seem to burst on to the scene, becoming apparent to the medical community quite suddenly.
retrovirus
uses RNA as a template for making DNA, which then inserts into a host chromosome.
reverse transcriptase
-retroviruses that carry molecules of an enzyme -catalyzes reverse transcription: the synthesis of DNA on an RNA template.
prions
infectious proteins that can cause brain diseases in animals.
three mechanisms that bacteria use to move genes from cell to cell
- Transformation is the uptake of DNA from the surrounding environment.
- Transduction is gene transfer by phages.
3. Conjugation is the transfer of DNA from a donor to a recipient bacterial cell.
