Flashcards in Unit #3: Chapters 10-16 Deck (143):
* cleavage of the cell into equal halves
-in animal cells – constriction of actin filaments produces a cleavage furrow
-in plant cells – plasma membrane forms a cell plate between the nuclei (then cellulose laid down for cell walls, with pectin between for the middle lamella)
-in fungi and some protists – mitosis occurs within the nucleus; division of the nucleus occurs with cytokinesis
* membrane wall that forms down middle of cell after mitosis in plant cells
* vesicles with membrane components fuse to each other and the cell wall
- egg cells and sperm cells
- contain half the number of chromosomes of an adult body cell
- produced from the process of meiosis
- haploid cells
- the fusion of two gametes
- produces a diploid zygote
* Chromosome division: spindle apparatus assembles, binds to the chromosomes and pulls the sister chromatids apart
* Mitosis is divided into 5 phases:
*Meiosis involves two successive cell divisions with no replication of genetic material between them. This results in a reduction of the chromosome number from diploid to haploid.
* Meiosis is characterized by 4 features:
1. Synapsis and crossing over
2. Sister chromatids remain joined at their centromeres throughout meiosis I
3. Kinetochores of sister chromatids attach to the same pole in meiosis I
4. DNA replication is suppressed between meiosis I and meiosis II.
* Meiosis produces haploid cells that are not identical to each other.
* Genetic differences in these cells arise from:
-random alignment of homologues in metaphase I (independent assortment)
(vs. Mitosis which produces 2 cells identical to each other.)
Genetic cross-over between non-sister chromatids
homologous chromosomes (homologues) become closely associated with each other
containing only 1 set of chromosomes
containing 2 sets of chromosomes
- diploid cell
- produced by sexual reproduction (by fertilization-the fusion of gametes)
* Step 1 of mitosis
-chromosomes continue to condense
-centrioles move to each pole of the cell (in animal cells)
-spindle apparatus is assembled at centrosomes at poles
-nuclear envelope dissolves
* Step 3 of mitosis
-microtubules pull the chromosomes to align them at the center of the cell
(metaphase plate: imaginary plane through the center of the cell where the chromosomes align)
- mostly a transitional stage in which all the preparations are checked before anaphase
* Step 4 of mitosis
-removal of cohesin proteins causes the centromeres to separate
-microtubules pull sister chromatids toward the poles (microtubules are gradually disassembled and therefore shortened)
-shortest phase (and irreversible)
-in anaphase A the kinetochores are pulled towards the poles
-in anaphase B the poles move apart (the cell becomes visibly elongated)
* Step 5 of mitosis
-spindle apparatus disassembles
-nuclear envelope forms around each set of sister chromatids
-chromosomes begin to uncoil (which permits gene expression)
-nucleolus reappears in each new nucleus
* Meiosis includes two rounds of division – meiosis I and meiosis II.
* During meiosis I, homologous chromosomes (homologues) become closely associated with each other. (This is synapsis.)
* Proteins between the homologues hold them in a synaptonemal complex.
* Physical exchange of regions of the chromatids
* The homologues are separated from each other in anaphase I.
In meiosis, metaphase I, homologues are arranged randomly with respect to which pair faces which pole (sometimes the maternal pair, sometimes the paternal pair).
* composed of chromatin (most chromosomes are about 40% DNA and 60% protein)
* every species has a different #
* compacted into soleniods in the nucleus
* must be replicated before cell division
Term for the synaptonemal complex - homologues paired closely along a lattice of proteins between them
having 2 of the same allele (gene from both parents is the same type: both brown eyes, purple flowers, etc.)
having 2 different alleles (gene from one parent is blue eyes, from other is brown eyes; or purple flower from one parent and white flowers from the other parent)
the form of each trait expressed in the F1 generation (offspring resulting from a cross of true-breeding parents)
the form of the trait not seen in the F1 generation (offspring resulting from a cross of true-breeding parents)
the heterozygote shows some aspect of the phenotypes of both homozygotes.
the heterozygote is intermediate in phenotype between the 2 homozygotes
total set of alleles of an individual
PP = homozygous dominant
Pp = heterozygous
pp = homozygous recessive
outward appearance of an individual
Inactive, condensed X chromosome in females
* Organelle that performs pre-mRNA splicing to remove non-coding (intron) sequences from the primary RNA transcript to produce the mature mRNA.
* Made of clusters of snRNP, which are snRNA and proteins.
Gene interaction where one gene can interfere with the expression of another.
dominant to recessive ratio in the F2 generation (Mendel discovered is actually 1:2:1 - 1 true-breeding dominant plant:2 non-true-breeding dominant plants:1 true-breeding recessive plant)
* the result of didybrid crosses
information for a trait passed from parent to offspring (coded in the DNA chromosomes from each parent)
alternate forms of a gene (such as blue eyes vs. brown eyes, purple flowers vs. white flowers
a cross used to determine the genotype of an individual with dominant phenotype
-cross the individual with unknown genotype (e.g. P_) with a homozygous recessive (pp)
-the phenotypic ratios among offspring are different, depending on the genotype of the unknown parent
* a cross to study only 2 variations of a single trait (has only 2 possible variations)
* all F1 generation resembled only 1 parent with the dominant variation (no offspring with characteristics intermediate between the 2 parents were produced)
* results in a 3:1 (1:2:1) dominant:recessive ration
* examination of 2 separate traits in a single cross
* The F1 generation of a dihybrid cross (RrYy) shows only the dominant phenotypes for each trait
* results in a 9:3:3:1 dominant:recessive ration
always result in the same traits from generation to generation
more than 2 options of a particular gene (such as variable heights, multiple hair colors, etc.)
an allele which has more than one effect on the phenotype (such as multiple symptoms for a disease)
sex (X) linkage
a trait determined by a gene on the X chromosome. associated with the sex of the individual.
Non-sex chromosomes (22 pairs in humans)
chromosomes which determine gender, such as X and Y in humans
The failure of homologues or sister chromatids to separate properly during meiosis
having an extra copy of a chromosome
nondisjunction that results in X gamete with a O gamete (no sex chromosome) resulting in an XO zygote individual. Phenotypes are a sterile, short female with webbed neck and low-normal mental capacity.
nondisjunction that results in XX gamete joining with a Y gamete resulting in an XXY zygote individual. Phenotypes are a male individual with some female body characters and reduced mental capacity
trisomy of chromosome 21
ABO blood types
The human ABO blood group system demonstrates:
-multiple alleles: there are 3 alleles of the I gene (IA, IB, and i)
-codominance: IA and IB are dominant to i but codominant to each other
sickle cell anemia
mutation of the protein hemoglobin, that leads to impaired oxygen delivery to tissues. confers greater resistance to malaria. recessive.
affects a protein involved in the chain of proteins that form blood clots. a hemophiliac can bleed to death from small cuts. x-linked recessive allele.
Traits that are not "one or the other", but can be expressed in many variations (human height)
* Polygenic inheritance occurs when multiple genes are involved in controlling the phenotype of a trait.
* The phenotype is an accumulation of contributions by multiple genes.
* These traits show continuous variation and are referred to as quantitative traits.
* For example – human height
* deoxyribose nucleic acid
* a nucleic acid chain of nucleotides (including thymine instead of uracil)
* ribose nucleic acid
* a nucleic acid chain of nucleotides (including uracil but not thymine)
* subunit of DNA and RNA
* 3 components:
- 5-carbon sugar (deoxyribose or ribose)
- a phosphate group
- a nitrogenous base (a purine (A or G) or a pyrimidine (T, C, or U (RNA only)))
DNA strands put together with opposing polar ends (5'-3' to 3'-5')
Hold the two strands of DNA together by the bases on opposite strands.
(A-T has 2 H bonds; G-C has 3 H bonds)
A pair of ester bonds that use the phosphate group of nucleotides to link them together.
Model of DNA most consistent with observations regarding chromosome replication. The chromosome strand splits into 2 strands, each of which are replicated by DNA polymerase.
Enzyme that forms the last phosphodiester bond between Okazaki fragments in DNA strand replication.
Enzyme responsible for matching the existing DNA bases on the template strand with complementary nucleotides and then linking the nucleotides together to make a new strand.
Make the DNA primer (see DNA primase)
An RNA polymerase enzyme that synthesizes short stretches of RNA on a DNA strand to function as primers for the DNA polymerase.
When genetic information is transferred between cells.
Performed experiments on mice to inject them with strains of pneumonia. Discovered transformation. Led to discovery that DNA holds the genetic material (not proteins).
Viruses that infect bacteria.
Two scientists who studied the question of proteins vs. DNA that contained genetic material. Used radioactive material on phages (viruses) to "flag" proteins and DNA to determine which were getting injected into bacteria, and therefore transferring genetic material.
Enzyme that acts to relieve the torsional strain (resulting in supercoiling) caused by unwinding DNA.
1. Proportion of Adenine always equals that of Thymine, and Guanine to Cytosine
2. Proportion of A-T to G-C varies by species
Obtained X-ray "pictures" of DNA fibers. Clearest confirmed that DNA was a helix and allowed calculation of the molecule (2 nm across with a complete helical turn every 3.4 nm).
DNA fragments synthesized discontinuously on the lagging strand.
The strand of DNA starting with the 3' end which can be replicated continuously (building the 5' to 3' sister strand).
The strand of DNA starting with the 5' end which must be replicated in sections (building the opposite 5' to 3' strand backwards as the strands are "unzipped").
In DNA replication, each parent strand is duplicated from the 3' end to the 5' end, but the strands are assembled antiparallel (opposing ends). So when the DNA molecule is split into two strands to be duplicated, the strand that starts with the 5' end (lagging strand) must be replicated in sections, starting from where the strands still meet, to where the last section started.
In DNA replication, each parent strand is duplicated from the 3' end to the 5' end, but the strands are assembled antiparallel (opposing ends). So when the DNA molecule is split into two strands to be duplicated, the strand that starts with the 3' end (leading strand) can be replicated continuously.
* DNA and RNA nucleotides are attached by phosphodiester bonds at the 5' carbon to the 3' hydroxyl group of the next unit. The "head" of the DNA strand has nothing attached to its phosphate group. (Contributes to polarity of the molecule.)
* DNA and RNA nucleotides are attached by phosphodiester bonds at the 5' carbon to the 3' hydroxyl group of the next unit. The "base" of the DNA strand has nothing attached to its hydroxyl group. (Contributes to polarity of the molecule.)
Watson & Crick
Determined the 3-D structure of DNA based on current evidence available (no testing of their own)
* Contains the transcribed DNA for translation to amino acids.
* The intermediary protein between mRNA and amino acids.
* Interprets information in the mRNA
* Helps position the amino acids on the ribosome.
* Critical to the functioning of the ribosome.
* To function, it must be able to bind to at least two charged tRNAs at once so that a peptide bond can be formed between their amino acids.
Produces a complementary copy of the DNA template strand (except T (thymine) is substituted with U (uracil)).
Performed by the enzyme RNA polymerase simultaneously with translation.
Performed by the enzyme RNA polymerase II in the nucleus.
One of the most complex and energy-intensive functions that cells perform.
The key organelle in translation, using mRNA and tRNA.
Binding site on a bacterial ribosome
* Binds to the tRNA attached to the growing peptide chain.
Binding site on a bacterial ribosome
* Binds to the tRNA carrying the next amino acid to be added.
Binding site on a bacterial ribosome
* Binds the tRNA that carried the previous amino acid added.
The basic unit of the genetic code; a sequence of three adjacent nucleotides in DNA or mRNA that codes for one amino acid.
* Each codon maps to exactly one amino acid. (There can be multiple codons that map to the same amino acid, but no amino acid maps to more than one codon.)
The 3-nucleotide sequence at the end of a tRNA molecule that is complimentary to, and base-pairs with, an amino-acid-specifying codon in mRNA.
Signals the end of a genetic code. Can be 1 of 3 different codon sequences: UAA, UGA, and UAG.
Third step in the elongation cycle of RNA translation. tRNA in the A site now has the peptide chain. As the mRNA is shifted to the next codon through the ribosome, the tRNA in the A site moves to the P site. The tRNA in the P site moves to the E site.
* noncoding DNA that interrupts the sequence of the gene.
The coding sequences that are expressed.
Site of gene transcription.
Site of gene translation.
* 2nd phase of the eukaryotic cell cycle
* synthesis of DNA (DNA replication) (irreversible stage)
- 2 sister chromatids are produced
* Following S phase, the sister chromatids appear to share a centromere, are held together by cohesin proteins, but are extended and uncoiled
- Proteins of the kinetochore are attached to the centromere.
Information passes in one direction from the gene (DNA) to an RNA copy of the gene, and the RNA copy directs the sequential assembly of a chain of amino acids into a protein.
Gene in the lac operon for beta galactosidase production
Enzyme that digests lactose into simple sugars glucose and galactose.
-p 45, 954?
Regulatory sites on DNA to control gene expression. Act as a roadblock to prevent the polymerase from initiating effectively.
Proteins that mediate negative control of gene expression.
* Bind to regulatory sites on DNA (operators).
* Respond to specific effector molecules.
* A short sequence found upstream of the start site and is therefore not transcribed by the polymerase.
* Forms a recognition and binding site for the RNA polymerase.
* In bacteria, two 6-base sequences are common: one at position -35 upstream and the other at -10. (Provides the site of initiation as well as the direction of transcription.)
The grouping of functionally related genes.
(Prokaryotic genes are often organized such that genes encoding related functions are clustered together.
The most common DNA-binding motif.
* Protein has 2 alpha-helical segments linked by a short, nonhelical segment (the "turn"). Each segment is held at right angles to each other. One holds the other (the recognition helix) in place.
* A zinc atom links an alpha-helical segment to a beta-sheet segment so the helical segment fits into the major groove.
* Subunits held together by leucines (amino acids) which holds their helical regions in a Y shape in the major groove (like a pair of tongs).
Binds to the 5' end of mRNA during transcription as a "5' cap". (Modified by the addition of a methyl group. The cap protects the 5' end of the mRNA from degradation and participates in translation initiation.)
* Composes chromosomes
* a complex of DNA and proteins
unexpressed regions of chromatin
expressed regions of chromatin
* a single strand of DNA
* sister chromatids: 2 copies of the chromosome within the replicated chromosome
* Adult body cells
* The eukaryotic cell cycle has 5 main phases:
1. G1 (gap phase 1)
2. S (synthesis) (irreversable stage)
3. G2 (gap phase 2)
(G1, S, and G2 are interphase)
4. M (mitosis) (anaphase is an irreversible stage)
5. C (cytokinesis)
* The length of a complete cell cycle varies greatly among cell types.
* The cell cycle is controlled at three checkpoints:
1. G1/S checkpoint
-the cell “decides” to divide
2. G2/M checkpoint
-the cell makes a commitment to mitosis
3. late metaphase (spindle) checkpoint
-the cell ensures that all chromosomes are attached to the spindle
* gap phase 1
* time of cell growth between cytokinesis and DNA replication
* cell undergos the majority of its growth - synthesizing proteins and creating organelles
* the longest phase
* gap phase 2
* fills the "gap" between DNA synthesis and mitosis
* some cell growth: synthesis of proteins and organelle development
* chromosomes undergo condensation, becoming tightly coiled.
* microtubles reorganize and begin to form spindles ( In animal cells, centrioles replicate and one centriole moves to each pole.)
* the state a cell can be in between G1 and S; a resting state
-the single, circular bacterial chromosome is replicated
-replication begins at the origin of replication and proceeds bidirectionally
-new chromosomes are partitioned to opposite ends of the cell
-a septum forms to divide the cell into 2 cells
* forms during cytokinesis
* in animal cells – constriction of actin filaments produces a cleavage furrow
In animal cells, an arrangement of microtubules to the nearby plasma membrane from centrioles after they have separated and moved to the poles.
The structure composed of microtubules radiating from the poles of the dividing cell that will ultimately guide the sister chromatids to the two poles.
microtubule-organizing centers (animal cells only)
* region of attachment of chromatids (attachment by cohesin proteins)
* G1 (gap phase 1) – time of cell growth
* S phase – synthesis of DNA (DNA replication)
- 2 sister chromatids are produced
* G2 (gap phase 2) – chromosomes condense
* Step 2 of Mitosis
-chromosomes become attached to the spindle apparatus by their kinetochores
-a second set of microtubules is formed from the poles to each kinetochore
-microtubules begin to pull each chromosome toward the center of the cell
prophase I (of meiosis)
-chromosomes coil tighter
-nuclear envelope dissolves
-homologues become closely associated in synapsis
-crossing over occurs between non-sister chromatids
metaphase I (of meiosis)
-terminal chiasmata hold homologues together following crossing over
-microtubules from opposite poles attach to each homologue, not each sister chromatid
-homologues are aligned at the metaphase plate side-by-side
-the orientation of each pair of homologues on the spindle is random
anaphase I (of meiosis)
-microtubules of the spindle shorten
-homologues are separated from each other
-sister chromatids remain attached to each other at their centromeres
telophase I (of meiosis)
-nuclear envelopes form around each set of chromosomes
-each new nucleus is now haploid
-sister chromatids are no longer identical because of crossing over
meiosis II (4 phases)
-prophase II: nuclear envelopes dissolve and spindle apparatus forms
-metaphase II: chromosomes align on metaphase plate
-anaphase II: sister chromatids are separated from each other
-telophase II: nuclear envelope re-forms; cytokinesis follows
The maternal and paternal copies of the same chromosome (such as "number 16").