Exam 1 Flashcards
1
Q
Test Cross
A
Cross dominant with recessive allele and look at the phenotypic ratio; requires at least two punnets squares
2
Q
Character
A
An observable feature i.e. Eye Color
3
Q
Trait
A
A specific form of a character i.e. Blue Eyes
4
Q
Allele
A
Different forms of a gene at a given locus on a chromosome
5
Q
Gene
A
Sequence of DNA which carries the information for a single polypeptide
6
Q
Parental Generation
A
The individuals that mate in a genetic cross. Their offspring are F1
7
Q
Monohybrid cross
A
A mating in which the parents differ with respect to the alleles of only on locus of interest
8
Q
Phenotype
A
The observable properties of an individual. What is “expressed”.
9
Q
Genotype
A
Exactly which alleles are present
10
Q
Particulate Theory
A
characteristics are passed from one generation to the next through discrete particles (genes) that retain their ability to be expressed, even though they may not appear in every generation - Mendel
11
Q
Diploid
A
Two sets of chromosomes, or two copies (homologs) of each chromosome
12
Q
Haploid
A
One set of chromosomes, Having a chromosome compliment consisting of one copy
13
Q
Genome
A
All the genetic info
14
Q
Central Dogma of Molecular Biology
A
Francis Crick: DNA –> RNA –> Protein
15
Q
Transcription
A
Nucleic Acid Language. The synthesis of RNA using one strand of DNA as a template.
16
Q
Translation
A
Nucleic Acid to Protein Language. The synthesis of a protein (polypeptide). Takes place of ribosomes, using the information encoded in Messenger RNA.
17
Q
Pre-MRNA
A
Initial Transcript in Eukaryotes. The initial gene transcript before it is modified to produce functional mRNA.
18
Q
Introns
A
In between the areas that are expressed. A portion of the gene within the coding region that is transcribed into pre -MRNA but is SPLICED OUT PRIOR TO TRANSLATION.
19
Q
Exons
A
Areas that are expressed. A portion of DNA molecule, in eukaryotes, that code for part of a polypeptide.
20
Q
Messenger RNA
A
Transcript of a region of one of the strands of DNA; carries information (as a sequence of codons) for the synthesis of one or more proteins.
21
Q
Ribosomal RNA
A
Involved in peptide bond formation
22
Q
Transfer RNA
A
A family of folded RNA molecules. Each tRNA carries a specific amino acid and anticodon that will pair with the complementary codon in mRNA during translation.
23
Q
Template
A
A molecule or surface where another molecule is synthesized
24
Q
RNA polymerase
A
An enzyme that catalyzes the formation of RNA from a DNA template
25
Promotor
A DNA sequence to which RNA polymerase binds to initiate transcription
26
Initiation
a
27
Elongation
The addition of monomers to make a longer RNA or protein during transcription or translation.
28
Termination
The end of transcription or translation
29
Splicosome
RNA-protein complex that splices out introns from eukaryotic pre-mRNA's
30
RNA splicing
The last stage of RNA processing in eukaryotes, where the tanscripts of introns are excised through the action of snRNP's
31
5' cap
a
32
Poly A tail
A long sequence of adenine nucleotides added after transcription to the 3' end of most eukaryotic mRNA's
33
codon
Three nucleotides in mRNA that direct the placement of a particular amino acid into a polypeptide chain
34
Silent mutations
no effect; caused by redundancy. A change in a gene's sequence that has no effect on the amino acid sequence of a protein because
1) it occurs in non-coding DNA
2) or does not change the amino acid specified by the corresponding codon
35
Nonsense mutations
Premature STOP codon in translation
36
Missense mutation
A change in a gene's sequence that changes the amino acid at that site in the encoded protein i.e Sickle Cell anemia
37
Frame-shift mutation
The addition or deletion of a single or two adjacent nucleotide's in a gene sequence. Results in the misreading of mRNA during translation and the production of a nonfunctional protein. Pretty often lethal
38
Initiation complex
a
39
Polysome
a
40
Signal Sequence
a
41
What is the difference btw Replication and Transcription?
1) Replication copies the entire genome
2) Replication only occurs before cell division in S phase of the cell cycle
3) Transcription copies only one or a few genes
4) Transcription occurs during G1 and G2 of cell cycle
42
Germline mutation
ccur in the cells of the germ line—the specialized cells that give rise to gametes (the eggs and sperm of sexual reproduction). A gamete with the mutation passes it on to a new organism at fertilization; Most detrimental
43
Conditional Mutations
A mutation that results in charecteristi phenotype only under certain enviornmental conditions.
44
Restrictive Conditions
a
45
Permissive Conditions
a
46
Point Mutations
A mutation that results from the gain, loss, or substitution of a single nucleotide.
1) Point mutations can arise because of errors in DNA replication that are not corrected during proofreading
2) or they may be caused by environmental mutagens: substances that cause mutations, such as radiation or certain chemicals.
3) some are loss-of-function or they can be silent mutations
47
Chromosomal Mutations (Spontaneous mutations)
Loss of or changes in position/direction of a DNA segment on a chromosome.
1) Deletion: the loss of a continuous segment of a gene or chromosome. Such mutations almost never revert to wild type.
2) Duplication: can be produced at the same time as deletions (FIGURE 9.17B). A duplication would arise if homologous chromosomes broke at different positions and then reconnected to the wrong partners. One of the two chromosomes produced by this mechanism would lack a segment of DNA (it would have a deletion), and the other would have two copies (a duplication) of the segment that was deleted from the first chromosome.
3) Inversions: an also result from the breaking and rejoining of chromosomes. A segment of DNA may be removed and reinserted into the same location in the chromosome, but “flipped” end over end so that it runs in the opposite direction. If either break site occurs within a gene, it is likely to cause a loss-of-function mutation in that gene.
4) Translocation: Translocations result when segments of chromosomes break off and become joined to different chromosomes. Translocations may involve reciprocal exchanges of chromosome segments, as in FIGURE 9.17D. Translocations often lead to duplications and deletions and may result in sterility if normal chromosome pairing cannot occur during meiosis.
48
Somatic mutations
Occur in the somatic (body) cells of a multicellular organism. These mutations are passed on to the daughter cells during mitosis, and in turn to the offspring of those cells. For example, a mutation in a single skin cell could result in a patch of skin cells that all have the same mutation. However, somatic mutations are not passed on to sexually produced offspring. (Exceptions occur in plants, where germline cells can arise from somatic cells and thus pass on somatic mutations.)
49
Loss-of-function mutations
- Codes for a nonfunctional protein
a result in either the loss of expression of a gene or in the production of a nonfunctional protein or RNA. Some loss-of-function mutations prevent a gene from being transcribed or cause transcription to terminate too soon. In other cases the gene is transcribed and translated, but the resulting protein no longer works as a structural protein or enzyme (as illustrated in Figure 9.16C). Loss-of-function mutations almost always show recessive inheritance in a diploid organism, because the presence of one wild-type allele usually results in sufficient functional protein for the cell. For example, the wrinkled seed phenotype studied by Mendel is due to a recessive loss-of-function mutation in the gene for starch branching enzyme 1 (SBE1). Even in plants with only one copy of the wild-type allele, there is enough SBE1 enzyme to produce the wild-type round phenotype.
50
Gain-of-function mutations
- Codes for a protein with a new function; doubles activity rate
- This kind of mutation usually shows dominant inheritance, because the presence of the wild-type allele does not prevent the mutant allele from functioning. This type of mutation is common in cancer. For example, a receptor for a growth factor normally requires binding of the growth factor (the ligand) to activate the cell division cycle. Some cancers are caused by mutations in genes that encode these receptors so that the receptors are “always on,” even in the absence of their ligands. This leads to the unrestrained cell proliferation that is characteristic of cancer cells.
51
What do all mutations have in common?
All mutations are alterations in the nucleotide sequence of DNA.
52
Sickle Cell
ther mutations result in altered amino acid sequences, and in some cases these changes can have drastic phenotypic effects. An example is the mutation that causes sickle-cell disease, a heritable blood disorder. The disease occurs in people who carry two copies of the sickle allele of the gene for human β-globin (a subunit of hemoglobin, the protein in human blood that carries oxygen). The sickle allele differs from the normal allele by one base pair, resulting in a polypeptide that differs by one amino acid from the normal protein. Individuals who are homozygous for this recessive allele have defective, sickle-shaped red blood cells
53
What do point mutations and chromosomal mutations have in common?
Like point mutations, chromosome mutations provide new combinations of genes and genetic diversity important to evolution by natural selection.
54
Spontaneous Mutation
are permanent changes in the genetic material that occur without any outside influence. In other words, they occur simply because cellular processes are imperfect. Spontaneous mutations may occur by several mechanisms:
1) DNA polymerase can make errors in replication. Most of these errors are repaired by the proofreading function of the replication complex, but some errors escape detection and become permanent.
2) The four nucleotide bases of DNA have alternate structures that affect base pairing. Each nucleotide can exist in two different forms (called tautomers), one of which is common and one rare. When a base temporarily forms its rare tautomer, it can pair with the wrong base (FIGURE 9.18A,C).
3) Bases in DNA may change because of spontaneous chemical reactions. One such reaction is the deamination (conversion of an amino group to a keto group) in cytosine to form the base uracil, which pairs with A rather than G. Usually these errors are repaired, but since the repair mechanism is not perfect, the altered nucleotide will sometimes remain and cause a permanent base change after replication.
4) Meiosis is not perfect. Sometimes errors occur during the complex process of meiosis. This can result in nondisjunction and aneuploidy (see Concept 7.4) or chromosomal breakage and rejoining (discussed above).
Gene sequences can be disrupted. Random chromosome breakage and rejoining can produce deletions, duplications, inversions, or translocations.
55
What do both spontaneous and induced mutations have in common?
The results of both spontaneous and induced mutations are permanent changes in the DNA sequence following replication.
56
Induced mutations
ccur when some agent from outside the cell—a mutagen—causes a permanent change in the DNA sequence:
- Some chemicals alter the nucleotide bases. For example, nitrous acid (HNO2) reacts with cytosine and converts it to uracil by deamination (FIGURE 9.18B). This alteration has the same result as spontaneous deamination: instead of a G, DNA polymerase inserts an A (see Figure 9.18C).
- Some chemicals add groups to the bases. An example is benzopyrene, a component of cigarette smoke that adds a large chemical group to guanine, making it unavailable for base pairing. When DNA polymerase reaches such a modified guanine, it inserts any one of the four bases, resulting in a high frequency of mutations.
- Radiation damages the genetic material. Radiation can damage DNA in three ways. First, ionizing radiation (including X rays, gamma rays, and particles emitted by unstable isotopes) can detach electrons from atoms or molecules and produce highly reactive chemicals called free radicals. Free radicals can change bases in DNA to forms that are not recognized by DNA polymerase. Second, ionizing radiation can also break the sugar–phosphate backbone of DNA, causing chromosomal abnormalities. And third, ultraviolet radiation (from the sun or a tanning lamp) can cause thymine bases to form covalent bonds with adjacent thymines. This, too, plays havoc with DNA replication by distorting the double helix, and can result in a mutation.
57
Transcription factors
Control whether or not a gene is active: repressors and activators. These proteins bind to specific DNA sequences at or near the promoter
58
What are the four stages of Development?
1) Determination
2) Differentiation
3) Morphogenesis
4) Growth
59
What is differentiation?
The process whereby originally similar cells follow different developmental pathways; the actual expression of determination.
*can be reversed under right conditions or early embryo
60
What is Morphogenesis?
Morphogenesis is the organization and spatial distribution of differentiated cells into the multicellular body and its organs. Morphogenesis can occur by cell division, cell expansion (especially in plants), cell movements, and apoptosis (programmed cell death). The different tissues specialize and work together for a common goal.
61
What is Growth?
Growth is the increase in size of the body and its organs by cell division and cell expansion. Growth can occur by an increase in the number of cells or by the enlargement of existing cells. Growth continues throughout the individual’s life in some organisms, but reaches a more or less stable end point in others.
62
What is totipotency?
Possessing all the genetic information and other capacities necessary to form an entire individual.
* Zygote
* eight cell stage
* genomic equivalence
63
What is pluripotent?
In later stages of the embryo, many cells are pluripotent (pluri, “many”); they have the potential to develop into most other cell types, but they cannot form new embryos.
* blastua
* undifferentiated
64
What is multi potent?
Through later developmental stages, including adulthood, certain stem cells are multipotent; they can differentiate into several different, related cell types. Mesenchymal stem cells (see above) are one kind of multipotent stem cell.
*gastrula
65
Blastula
Limited pluripotent
66
Gastrula
Multipotent
67
What are the two ways in which cell fate can be determined?
1) by the asymmetrical distribution of cytoplasmic factors inside a cell, so that its two progeny cells receive unequal amounts of the factors, or
2) by the differential exposure of two cells to an external signal (an inducer).
68
What are cytoplasmic determinants
Cytoplasmic determinants include specific transcription factors that promote differential gene expression in the two daughter cells. They also include small regulatory RNAs and mRNAs, which also contribute to differential gene expression.
69
Differential gene transcription is a hallmark of cell differentiation
An important mechanism by which cells differentiate into specific cell types, with specific functions, is differential gene transcription. One well-studied example of cell differentiation is the conversion of undifferentiated muscle precursor cells (myoblasts) into the cells that make up muscle fibers (FIGURE 14.10). A key event in the commitment of these cells to become muscle is that they stop dividing. Indeed, in many parts of the embryo, cell division and cell differentiation are mutually exclusive. Cell signaling activates the gene for a transcription factor called MyoD (myoblast-determining gene). MyoD activates the gene for p21, an inhibitor of cyclin-dependent kinases (CDKs) that normally stimulate the cell cycle at G1 (see Figure 7.10). Expression of the p21 gene causes the cell cycle to stop, and other transcription factors then enter the picture so that myoblasts can differentiate into muscle cells.
70
What are the four organs in plants?
sepals, petals, stamens (male reproductive organs), and carpels (female reproductive organs).
71
What is the meristem?
Plant tissue made up of undifferentiated actively dividing cells.
72
homeotic genes
homeotic genes
73
genetic switches
echanisms that control how the genetic toolkit is used, such as promoters and the transcription factors that bind them. The signal cascades that converge on and operate these switches determine when and where genes will be turned on and off.
74
heterotypy
Alteration in a developmental regulatory gene itself rather than the expression of the genes it controls.
legs in arthropods
