Chapter 9-11 Flashcards
(209 cards)
1
Q
Genetic counselling
A
provision of expert advice to prospective and actual parents about risks of occurrence or recurrence of inherited disorders
2
Q
Genes determine our…
A
characteristics (phenotypes)
3
Q
Genes are passed on from…
A
generation to generation
4
Q
In our body we have how many sets of genes
A
double set, one from mother, one from father
5
Q
Gamete
A
a haploid cell, that is able to unite with a gamete of the opposite sex to form a zygote
6
Q
Haploid
A
a cell that has one copy of each specific chromosome
7
Q
Cell cycle
A
is a set of events that occur cyclically that lead to the repeated replication of the eukaryotic cell
8
Q
Cell cycle phases
A
G0 (resting), G1 (growth 1), S (synthesis), G2 (growth 2), M (mitosis/meiosis + cytokinesis)
9
Q
What happens in S
A
DNA is duplicated as a result of the chromosomes duplicating
10
Q
Important thing about cell cycle
A
only dividing cells are in the cell cycle, others are in G0
11
Q
Meiosis
A
process of nuclear division that results in the production of new haploid cells
12
Q
Mitosis
A
the process of nuclear division resulting in giving rise to two identical daughter cells.
13
Q
Binary fission (where, results in, asexual or sexual)
A
where: prokaryotic cells
results in: exact copies of the cells (assuming there are no mutations)
is it asexual/sexual: asexual
14
Q
Binary fission process
A
- DNA replication occurs, the single circular chromosomes relocates into two circular chromosomes (Presumably plasmids and ribosomes replicate)
- the twin chromosomes attach to opposite poles of the cell membrane
the cell begins to elongate, dragging the chromosomes to opposite ends - the cell membrane and walk invaginated upon itself
- the parent cell splits into two daughter cells as the cell membrane and wall separates the two new parent cells
15
Q
Sexual cell reproduction involves
A
the fusion of gametes
16
Q
Regulator genes
A
genes that produce proteins that control the action of other genes and these actions determine whether other genes are active (‘on’) or not (‘off’) and, if active, the rate at which their products are made.
17
Q
Two ways that regulator gene proteins can act
A
DNA-binding proteins, signalling proteins
18
Q
DNA-binding proteins
A
bind to regions of nuclear DNA near genes and directly switch these genes on or off (net positive charge)
19
Q
Signalling proteins
A
bind to receptors on the membrane of cells in their target tissue and trigger a series of intercellular reactions that switch genes on or off
20
Q
Human genome project
A
international project directed at the identification of the sequence of the more than three billion bases in the human genome.
21
Q
Aim of human genome project
A
store the sequences in a data base to create a map of all the human genes.
22
Q
Results caused by human genome project (5)
A
insights into diagnosis, treatment, prevention, human biology, evolution
23
Q
The nature of genetic code
A
the genetic code consists of triplet base sequences, code is non-overlapping (e.g. 12 bases = only 4 triplets), said to be universal (virtually same in plants/animals/bacteria), is redundant (more than one triplet codes for same thing), information encoded in DNA is instructions to assemble polypeptides from amino acids, includes start and stop codons
24
Q
Start codon
A
TAC
25
Number of stop codons
3
26
Stop codons
ATT, ATC, ACT
27
Genetic code
non-overlapping triplet code consisting of groups of three bases. The sequence of nucleotides, coded in triplets (codons) along the mRNA, which determines the sequence of amino acids in protein synthesis.
28
DNA sequence definition
relative order of base pairs, whether in a fragment of DNA, a gene, chromosome or an entire genome.
29
Gene
the fundamental physical and functional unit of heredity made of DNA. A gene is an ordered sequence of nucleotides located in a particular position on a particular chromosome that encodes a specific functional product
30
Gene expression
The process by which a gene's coded information is converted into the structures present and operating in the cell. Expressed genes include those that are transcribed into mRNA and then translated into protein and those that are transcribed into RNA but not translated into protein (e.g., transfer and ribosomal RNAs).
31
Introns
The DNA base sequences interrupting the protein-coding sequences of a gene; these sequences are transcribed into RNA but are cut out of the message before it is translated into protein.
32
Exons
The protein-coding DNA sequences of a gene
33
Transcription
The synthesis of an RNA copy from a sequence of DNA (a gene); the first step in gene expression.
34
Translation
The process in which the genetic code carried by mRNA directs the synthesis of proteins from amino acids.
35
tRNA
A class of RNA having structures with triplet nucleotide sequences that are complementary to the triplet nucleotide coding sequences of mRNA.
36
Role of tRNA
to bond with amino acids and transfer them to the ribosomes, where proteins are assembled according to the genetic code carried by mRNA.
37
Promoter
a site on DNA to which RNA polymerase will bind and initiate transcription.
38
Polymerase (DNA/RNA)
Enzymes that catalyse the synthesis of nucleic acids on preexisting nucleic acid templates, assembling RNA from ribonucleotides or DNA from deoxyribonucleotides.
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Primer
Short preexisting polynucleotide chain to which new deoxyribonucleotides can be added by DNA polymerase.
40
DNA replication
The use of existing DNA as a template for the synthesis of new DNA strands. In humans and other eukaryotes, replication occurs in the cell nucleus.
41
Karyotypes
graphic display of the complete set of chromosomes from a cell of a particular organism.
42
Ideogram
stylised representation of a haploid set of chromosomes arranged in order of decreasing size.
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Autosomal chromosomes
homologous pairs that does not differ between the sexes
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Autosomes can be distinguished by (3)
relative size, position on centromere, patterns of light and dark bands with special staining techniques
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Sex chromosomes
determine the sex of the organism
46
Somatic cells (colloquial)
body cells
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Mitosis
nuclear division of a somatic cell resulting in two identical daughter cells
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Stages of Mitosis
(I) PMAT
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Stages of Meiosis
(interphase i), prophase i, metaphase i, anaphase i, telophase i, cytokinesis i, prophase ii, metaphase ii, anaphase ii, telophase ii, cytokinesis ii
50
Interphase
G1, S, G2
51
Prophase
chromatin shortens and thickens into small compact chromosomes, spindle forms the centrosomes around the nucleus and approaches the nucleus, nuclear membrane breaks down
52
Metaphase
chromosomes align in a plane along the middle of the nucleus, the spindle attaches to the centromeres of the chromosome
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Anaphase
spindle contracts, separating each double stranded chromosome into two single stranded chromosomes, and the single stranded chromosomes migrate to opposite poles of the cell, attached to the spindle
54
Telophase
the chromosomes uncoil and become less compact (decondense), two nuclear membranes reform
55
Cytokinesis
cytoplasm splits to identical daughter cells
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When does crossing over occur
occurs in prophase i of meiosis
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Aneuploidy
not the right number of chromosomes
58
Polyploidy
whole set of chromosomes fail to disjunct
59
Congenital disorders caused by…
mistakes in chromosome numbers and chromosomes abnormalities
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Non-disjunction definition
when an error occurs in separation of chromosomes
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Non-disjunction in 1st stage affects...
all 4 cells
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Non-disjunction in 2nd stage affects...
2 only
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Gonads
organs where gametes are formed
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Germline cells
cells that give rise to gametes
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How is zygote formed
nucleus of sperm fuses to nucleus of egg
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What are the only cells to cross the genetic gap
gametes; all other cells die when the cell dies
67
Somatic cells definition
cells of the body that are diploid
68
How is DNA transmitted across generations
through gametes
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Chromosomes
thread-like structures composed of DNA and protein
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Chromosomes are only visible (under a microscope) during…
meiosis and mitosis
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Chromosome map
drawing of a chromosome showing the gene loci
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Structure of chromosome
- has a centromere in the centre of the chromosomes
- kinetochore
- has a telomere at ends
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The centromere has ….
constriction
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Kinetochore (3)
surrounds the centromere, made of protein, forms the attachment points for spindle fibres necessary for movement
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Telomere
DNA made up of thousands of repeats of sequences of base pairs
Telomere role - prevent chromosomes sticking together and they enable complete replication of chromosomes to occur.
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Human telomere sequence
TTAGGG
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Chromatids
two strands replicated chromosome which are joined together by a single centromere
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Centromere
constricted part of the chromosome that contains the region where spindle fibres attach during meiosis and mitosis.
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Loci/locus
the position of a gene on a chromosome
80
Linked genes are
on the same chromosome
81
Linkage groups are
refers to chromosomes, usually equal to haploid number of chromosomes.
82
Homologous chromosomes
a pair of chromosomes containing the same linear gene sequences, each derived from one parent. (but different alleles)
83
The larger the chromosome...
the more genes located on it
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Chromosome mutations
include gross structural alterations of chromosomes, changes in numbers of chromosomes
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Gross structural alterations of chromosomes
includes translocation, inversions, duplication/deletion of sections of the chromosome
86
Translocation
a section of one chromosome attaches to the end of another chromosome.
87
Inversions
single chromosome undergoes breakage and a segment of the chromosome is reversed end to end (do not cause abnormalities in carriers as long as it is balanced with no extra/missing info)
88
Changes in number or chromosomes is caused by
non-disjunction
89
Non-disjunction causes...
aneuploidy and polyploidy organisms
90
Aneuploidy
abnormal number of chromosomes
91
Examples of aneuploidy
abnormal number of chromosomes
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Polyploidy
whole sets of chromosomes do not separate during meiosis
93
Karyotypes
graphic display of the complete set of chromosomes from a cell of a particular organism.
94
Autosomal chromosomes
homologous pairs that does not differ between the sexes
95
Genome
the full set of genes of an individual
96
Alleles
alternative forms/variants of a particular gene that controls one function
97
Genotype
refers to both the double set of genetic instructions present in a diploid organism and to the genetic makeup of an organism at one particular gene locus
98
Phenotype
expression of an organism’s genotype in its structural, biochemical and physiological characteristics
99
Heterozygote
the presence of different alleles at one or more loci on homologous chromosomes
100
Homozygote
an individual with both identical alleles (versions of a single gene) at one locus (position).
101
Polygenes
many genes that work together to produce a trait.
102
Polygenes cause… (type of variation)
continuous variation
103
Continuous variation
results in characteristics which exhibit a continuos range of traits (phenotypes) across a population.
104
Examples of continuous variation
height, skin colour, eye colour.
105
Discontinuous variation
in a population occurs when members of a population can be grouped into a few discrete and non-overlapping classes with regard to expression of a trait
106
Example of discontinuous variation
number of fingers
107
Monomorphic population
all members have identical phenotypic trait
108
Polymorphic population
members have several variants of particular trait
109
Mutation
permanent change in the genetic material (or DNA sequence).
110
Important to remember about mutation
spontaneous events
111
Environment effect of genes can be either..
either internal or external
112
Examples of environment effect on genes (2)
chemicals in external environment cause birth defects/alter appearance, absence of chemical in body - trait not expressed e.t.c.
113
Test cross
a cross between an organism of interest (that exhibits the dominant trait) and an organism with a known recessive phenotype, in order to determine the genotype of a particular trait in the organism of interest, or if two genes are linked.
114
Pedigree
a “family tree” that shows the frequency and occurrence of particular phenotypes (hence alleles) over many generations
115
Symbol for male
square
116
Symbol for female
circle
117
Symbol for twins identical vs fraternal
identical has line through middle, fraternal has no line
118
Identify if recessive
skips generation, both parents have it then all children have it
119
Identify if sex-linked dominant pedigree
father = all daughters, if a son = mother must have
120
Identify if sex-linked recessive
father has = all daughter, mother has = all sons
121
Sex-linked trait
an allele (gene) that is found on the sex chromosomes (usually X)
122
Hemizygous
for sex-linked trait: carrier, normal, affected
123
Important to note for sex-linked phenotype
List gender + phenotype
124
Lethal allele
the homozygous genotype is lethal
125
How to know if gene is linked or not
if phenotypic ratio varies from the expected, it is linked
126
Down’s syndrome
extra copy of the 21 chromosome
127
WZ/ZZ in what animals
some birds, some snakes (tiger), monitor lizards (goannas), amphibians (frog),
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Egg production in females called
Oögenesis
129
Oögenesis how many eggs produced each stage
two then only one, two then only one
130
Sperm production in males called
Spermatogenesis
131
Spermatogenesis how many eggs produced in each stage
2, so four in total at end
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Asexual reproduction
production of genetically identical offspring from one parental organism only.
133
Sexual reproduction
method of producing offspring that involves a genetic contribution (usually) from two parents, typically the fusion of a haploid egg and a haploid sperm to form a diploid zygote.
134
Recombination
process of generating new combinations of alleles of various genes both by crossing over and by independent assortment during meiosis.
135
Number of genes in each cell
21,000
136
Mitochondrial genes
genes located in the DNA of mitochondria and transmitted in a matrilineal manner
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Multiple alleles
refers to three or more alleles of a specific gene
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Heterozygous
a cell/organism whose genotype for a particular gene comprises two different alleles
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Homozygous
cell/organism whose genotype for a particular gene comprises of two identical alleles
140
Dominant
refers to a trait that is expressed in the heterozygous condition
141
Recessive
refers to a trait that is only expressed in the homozygous form i.e. is not expressed in the heterozygous form.
142
Sex-linked trait
refers to a trait which is controlled by a gene with its locus on a sex-chromosome
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Two types of sex-linked traits
x linked and y linked
144
How to find out which trait is dominant
the phenotype of the heterzygote
145
X-inactivation
random switching off of one gene of the two X-chromosomes present in somatic cells of mammalian females
146
When does x-inactivation occur
during early embryonic development.
147
Carrier
heterzygote that has the allele for the recessive trait but does not express the trait
148
Co-dominance
relationship between two alleles of a gene, where the alleles are equally dominant, such that a heterozygous organism shows the expression of both alleles in its phenotype.
149
Difference between co-dominance and incomplete dominance red/white flower
co-dominance would be red and white dots, incomplete dominance is pink flower
150
The genotype + environment forms
the phenotype
151
Why test crosses are used
to identify if organism showing a dominant trait is homozygous or heterozygous, establish linkage relationships
152
To work out if a trait is dominant homozygous minimum organisms to be born
16
153
Ways linked genes are represented
A b (_) a B, Ab/aB, A b (_=) a B
154
Test to work out if gene is linked
cross two heterozygotes
155
If the gene is linked for heterozygous test, the ratio will be
9:3:3:1
156
If it is not linked, the ratio for heterozygous test will be
1:1:1:1
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Gene assortment
independent distribution of unlinked genes to gametes as a result of the independent movement of non-homologous chromosomes carrying those genes to opposite poles during meiosis.
158
Distance between loci formula
100*number of recombinant offspring/total number of offspring
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What did Mendel study
inheritance of variation in the traits
160
What lead to Mendel’s success
one trait at a time, known history of parents, recording parentage, counting offspring
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What do large numbers of offspring allow (3)
egularities to be recognised and valid averages to be identified, to ‘ascertain their statistical relations’
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Mendel’s discoveries (7)
each trait controlled by a pair of inherited factors (alleles). For each trait individual plants had two factors that could be identical or different, plants with identical factors were referred to as pure breeding and plants with different factors were called hybrids. Each factor was a discrete particle and retained its identity across generations. Recessive and Dominant. One factor per gamete. Genes behaved independently. The results were the same regardless of plant was used as male/female.
163
Transforming factor
substance that had the ability to change the genetic character of bacteria that was later identified as being DNA?
164
Dissociation
separation of double-stranded DNA molecule into its single strands, which occurs when the hydrogen bonds stabilising the two strands are broken.
165
Re-association
re-pairing of single strands of DNA during cooling after the two strands of a DNA double helix have been dissociated by heating.
166
Hybridisation
pairing between single-stranded complementary DNA segments from organisms from the same or even different species.
167
Genome
the full set of genes carried by an individual (or cell)
168
Gene sequencing
identification of the order or sequence of bases along the DNA of a specific gene
169
Decoded
refers to the translation of genetic information held in DNA into amino acids
170
Encoded
refers to the holding of genetic information in DNA in coded form as a base sequence.
171
Genomics
study of genomes
172
Proteome
full set of proteins produced by a single cell or organism
173
Single nucleotide polymorphism
when one base sequence varies.
174
Opening reading frames
reading frames (codes) that can be transcribed
175
Name of genes that result in proteins
protein-encoding genes
176
Gene duplication
where a second copy if the DNA sequence of a gene appears in a genome.
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Gene action
processes of transcription and translation of a gene into a gene product.
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Transcription steps
1. RNA polymerase attaches to a specific promotor sequence of DNA in the upstream region of the template strand. The double-stranded DNA of the strand unwinds and exposes the bases of the template strand.
2. The base sequence of the DNA template guides the building of a complementary copy of the mRNA sequence. The RNA polymers enzyme moves along the DNA template in a 3’ to 5’ direction and, as it moves, complementary nucleotides are brought into place, and, one by one, are mined to form an RNA chain.
3. After the RNA polymerase moves past the coding region and into the down-stream region of the gene, transcription stops and the mRNA molecule is released from the template. The result of this process is a single stranded molecule of pre mRNA.
179
What happens after transcription
pre-mRNA is modified into mRNA
180
What is modification of pre-mRNA called
post-transcription modification
181
What happens in post-transcription modification
introns are cut out, poly-A tail added to 3’ end and a methyl cap is added to 3’ end
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How are introns spliced
spliceosomes
183
Where does translation occur
ribosomes (cytoplasm)
184
How are amino acids bought to mRNA
tRNA
185
tRNA structure
tRNA consists of a strand of 76 nucleotides coiled and pairs with themselves. At one end of the tRNA molecule there are three bases that make up an anticodon, at the other end is a region that attaches to one specific amino acid
186
What does amino acyl tRNA synthetase do
catalyses the linking of each amino acid to its specific tRNA carrier.
187
Codon
sequences of 3 bases
188
DNA is a… model
semi-conservative model
189
Some genes are active only
in specific tissues
190
Pre mRNA also known as
primary transcript
191
Two steps in gene expression
transcription, translation
192
RNA polymerase role
unwind DNA and synthesise an RNA strand complementary to the 3’-5’ direction of the gene
193
G1 phase
cell grows in size, duplicating its organelles, synthesised proteins required for S phase
194
G2 phase
grows in size again, and synthesising proteins for M
195
M
mitosis/meiosis
196
DNA replication
- DNA helicase unwinds DNA
- primer is synthesised by RNA/DNA primes
- DNA polymerase synthesises a new DNA strand starting from the primers (5’-3’) small segments backwards (Okazaki fragments)
- leading strand? lagging strand?
- DNA ligase join fragments in each strand to form DNA strand
197
Silent mutations
no change in amino acid sequences
198
Missense mutations
replacement of one amino acid with another
199
Nonsense mutations
mutated into a stop codon
200
Gene amplifications
segments of DNA are repeated again
201
Prophase 1
chromatin shortens and thickens into small and compact chromosomes, the spindle forms the centrosomes around the cycles and approaches the nucleus, the chromosomes line up in their homologous chromosomes and cross over, the nuclear membrane breaks down
202
Metaphase 1
spindle fibres attach to the centromeres of each homologous chromosome, the tetrads line up in a plane in the middle of the cell
203
Anaphase 1
the spindle contracts, separating each tetrad back into the double stranded chromosomes, and the double stranded chromosomes migrate to opposite poles of the cell attached to the spindle
204
Telophase 1
chromosomes uncoil and become less compact, two nuclear membranes reform,
205
Meiosis 2 stages are the same as...
mitosis 1 stages
206
Identical twins are also known as
monozygotic twins
207
Genotypic ratio
expected ratio of offspring with each possible genotype
208
Phenotypic ratio
expected ratio off offspring with each possible phenotype
209
Difference between prokaryote and eukaryotes chromosomes
Prokaryotes are circular, eukaryotes are linear
Prokaryotes don't have introns
Prokaryotes lack histones
