Bio 5: Cellular Control Flashcards
Gene
Length of DNA that codes for one or more polypeptides
Polypeptide
Polymer consisting of a chain of amino acids residues joined by peptide bonds
Protein
Large polypeptide usually 100 or more amino acids. Some proteins consist of one polypeptide chain and some consist of more than one polypeptide chain.
Transcription
mRNA is used.
Hydrogen bonds break
Catalysed by RNA polymerase
Translation
Assembly of polypeptides at ribosomes. The sequence is dictated by codons on mRNA.
Mutation
Change in the amount of, or arrangement of the genetic material in a cell
Chromosome mutations
Changes to the structure of chromosomes and/or to their number
DNA mutation
Changes to the genes due to changes in nucleotide base sequences
Point mutation/substitutions
One base pair replaces another
Insertion/deletion (frameshift)
One or more nucleotide pairs are inserted or deleted from a length of DNA
Huntington disease
Expanded triple nucleotide repeat
Normal gene for Huntington protein - repeating CAG
Symptoms include dementia, loss of motor control
Sickle cell anaemia
Point mutation on triplet 6 of the beta chains for haemoglobin.
Cystic Fibrosis
Deletion of tripled base pairs, deleting an amino acid in the normal polypeptide
Allele
An alternative version of a gene. At the same locus on the chromosome and codes for the same polypeptide but the change can alter the proteins structure.
Silent mutation
The base triplet has changed but it still codes for the same amino acid, the protein is unchanged
Operon
A length of DNA made up of structural genes and control sites.
Structural genes
Codes for beta-galactosidase and lactose permease
Each has base pairs that can be transcribed into a length of mRNA
Control sites
Operator region: switches on and off structural genes
Promoter region: RNA polymerase binds to it to begin the transcription of the the structural genes
Homeobox genes
Controls the development of the body plan of an organism, including polarity and positioning of the organs
Apoptosis
Programmed cell death
Enzymes break down cytoskeleton Cytoplasm is dense Membrane can changes to blebs Chromatin condenses Nuclear envelope breaks Breaks into vesicles Taken up by phagocytosis
Meiosis
Reduction division
Four daughter cells
Half the number of chromosomes
They are haploid
Bivalent
Pair of joined homologous chromosomes
Chiasmata
The points where non-sister chromatids within a bivalent join, where they cross over
Locus
Position of a gene on a chromosome
Crossing over
Prophase I
Non sister chromatids wrap and join at Chiasmata
Chromosomes break here
They rejoin their non sister chromatid in the same bivalent
Reassortment of chromosomes
Consequence of random distribution of maternal and paternal chromosomes at the equator
Each gamete is a different mixture of maternal and paternal
Reassortment of chromatids
Alignment at metaphase II determines their segregation at anaphase II
(After crossing over they are no longer identical)
Fertilisation
One ovum and 300 million spermatozoa
All genetically different
Genotype
The allele present within cells of an individual for a particular trait or characteristic
Autos ones
Chromosomes not concerned with determining sex
Homozygous
Two identical alleles for a gene
Heterozygous
Two different alleles of the same gene
Phenotype
Observed characteristics in an organism
Dominant
An allele is dominant if it is always expressed in the phenotype
Recessive
It is recessive if it is only expressed in the phenotype in the presence of another identical allele, or in the absence of a dominant allele
Codominant
Two alleles of the same genes are described as Codominant if they are both expressed in the phenotype of a heterozygote
Linkage
Two or more genes that are located on the same chromosome
They are normally inherited together because they don’t separate in meiosis
Sex linkage
A characteristic is sex linked if the genes that codes for it is in the sex chromosomes
Haemophilia A
Clotting factors
- factor VIII coded by a gene on X chromosome
Recessive allele expresses an altered protein
Increase in clotting time
Females with the recessive allele - carriers
Males with the recessive allele - haemophilic
Duchenne muscular dystrophy
DMD gene for muscle protein dystrophin is on the X chromosome
Boys often get muscle weakness in early childhood
Wheelchair by 10
Death due to complications by 20s
Sickle cell anaemia
Beta haemoglobin differ by one amino acid
When this haemoglobin is deoxygenated it becomes deformed and inflexible
After many cycles they becomes unusable
Epistasis
The interaction of different gene loci so that one gene locus masks or suppresses the expression of another gene locus
Antagonistic recessive Epistasis
The presence of a homozygous recessive gene at one locus prevents the second from being expressed even if the second is dominant.
The alleles at the first locus are described as Epistasic and those at the second are described as hypostatic
9:3:4 ratio
Antagonistic dominant Epistasis
The dominant allele at one locus prevents the expression of the gene at the second locus. The presence of one dominant allele at the first locus will mask the expression at the second even if the at the second there is homozygous dominant alleles.
12:3:1 or 13:3
Complementary Epistasis
Two genes at different loci need to be present in order to cause a particular phenotype.
Example:
C-R- = purple
Chi squared
Statistical test to find out if the difference between observed data and expected data is small enough to be due to chance
Discontinuous variation
Clear categories
Qualitative differences
Different alleles at a single locus have large effects on locus
Different gene loci have different effects on the phenotype
Continuous variation
Quantitative differences
Traits that have continuous variation are controlled by two or more traits
Population
A group of individuals of the same species that can interbred
The Hardy Weinberg principle
To calculate allele frequencies
Assumes: Population is large Mating random No selective advantage for any genotype No mutation, migration or genetic drift
Selection pressure
An environmental factor that confers greater chances of survival to reproductive age on some members of the population
Stabilising selection
A type of natural selection in which allele and genotype frequency within populations stays the same because the organisms are already well adapted to their environment
Genetic drift
The change in allele frequency in a population as some alleles pass to the next generation and some disappear. This causes some phenotypic traits to become rarer or more common
Biological species concept
A group of similar organisms that can interbred and produce fertile offspring
Phylogenetic species concept
A group of organisms that has similar shape, biochemistry, stages of development and behaviour. They also occupy the same ecological niche.
Monophyletic group
One that includes an ancestral organism and all its descendants
Paraphyletic group
Includes the most recent ancestor but not all its descendants.
Reptiles is Paraphyletic as it exclude birds which are descendants of reptiles
Natural selection
The organisms that are best adapted to their environment are more likely to survive. The favourable alleles are passed to their offspring.
Artificial selection
Where humans select the animals with the desirable characteristics. They allows these animals to breed so therefore the offspring have the characteristics wanted.
In cows: Milk yield measured Progeny of bulls tested to see which have high milk yield daughters Artificial insemination Hormones to make many eggs Invitro fertilisation Surrogates
Translation
Assembly of polypeptides at ribosomes. The sequence is dictated by codons on mRNA.
Mutation
Change in the amount of, or arrangement of the genetic material in a cell
Chromosome mutations
Changes to the structure of chromosomes and/or to their number
DNA mutation
Changes to the genes due to changes in nucleotide base sequences
Point mutation/substitutions
One base pair replaces another
Insertion/deletion (frameshift)
One or more nucleotide pairs are inserted or deleted from a length of DNA
Huntington disease
Expanded triple nucleotide repeat
Normal gene for Huntington protein - repeating CAG
Symptoms include dementia, loss of motor control
Sickle cell anaemia
Point mutation on triplet 6 of the beta chains for haemoglobin.
Cystic Fibrosis
Deletion of tripled base pairs, deleting an amino acid in the normal polypeptide
Allele
An alternative version of a gene. At the same locus on the chromosome and codes for the same polypeptide but the change can alter the proteins structure.
Silent mutation
The base triplet has changed but it still codes for the same amino acid, the protein is unchanged
Operon
A length of DNA made up of structural genes and control sites.
Structural genes
Codes for beta-galactosidase and lactose permease
Each has base pairs that can be transcribed into a length of mRNA
Control sites
Operator region: switches on and off structural genes
Promoter region: RNA polymerase binds to it to begin the transcription of the the structural genes
Homeobox genes
Controls the development of the body plan of an organism, including polarity and positioning of the organs
Apoptosis
Programmed cell death
Enzymes break down cytoskeleton Cytoplasm is dense Membrane can changes to blebs Chromatin condenses Nuclear envelope breaks Breaks into vesicles Taken up by phagocytosis
Meiosis
Reduction division
Four daughter cells
Half the number of chromosomes
They are haploid
Bivalent
Pair of joined homologous chromosomes
Chiasmata
The points where non-sister chromatids within a bivalent join, where they cross over
Locus
Position of a gene on a chromosome
Crossing over
Prophase I
Non sister chromatids wrap and join at Chiasmata
Chromosomes break here
They rejoin their non sister chromatid in the same bivalent
Reassortment of chromosomes
Consequence of random distribution of maternal and paternal chromosomes at the equator
Each gamete is a different mixture of maternal and paternal
Reassortment of chromatids
Alignment at metaphase II determines their segregation at anaphase II
(After crossing over they are no longer identical)
Fertilisation
One ovum and 300 million spermatozoa
All genetically different
Genotype
The allele present within cells of an individual for a particular trait or characteristic
Autos ones
Chromosomes not concerned with determining sex
Homozygous
Two identical alleles for a gene
Heterozygous
Two different alleles of the same gene
Phenotype
Observed characteristics in an organism
Dominant
An allele is dominant if it is always expressed in the phenotype
Recessive
It is recessive if it is only expressed in the phenotype in the presence of another identical allele, or in the absence of a dominant allele
Codominant
Two alleles of the same genes are described as Codominant if they are both expressed in the phenotype of a heterozygote
Linkage
Two or more genes that are located on the same chromosome
They are normally inherited together because they don’t separate in meiosis
Sex linkage
A characteristic is sex linked if the genes that codes for it is in the sex chromosomes
Haemophilia A
Clotting factors
- factor VIII coded by a gene on X chromosome
Recessive allele expresses an altered protein
Increase in clotting time
Females with the recessive allele - carriers
Males with the recessive allele - haemophilic
Duchenne muscular dystrophy
DMD gene for muscle protein dystrophin is on the X chromosome
Boys often get muscle weakness in early childhood
Wheelchair by 10
Death due to complications by 20s
Sickle cell anaemia
Beta haemoglobin differ by one amino acid
When this haemoglobin is deoxygenated it becomes deformed and inflexible
After many cycles they becomes unusable
Epistasis
The interaction of different gene loci so that one gene locus masks or suppresses the expression of another gene locus
Antagonistic recessive Epistasis
The presence of a homozygous recessive gene at one locus prevents the second from being expressed even if the second is dominant.
The alleles at the first locus are described as Epistasic and those at the second are described as hypostatic
9:3:4 ratio
Antagonistic dominant Epistasis
The dominant allele at one locus prevents the expression of the gene at the second locus. The presence of one dominant allele at the first locus will mask the expression at the second even if the at the second there is homozygous dominant alleles.
12:3:1 or 13:3
Complementary Epistasis
Two genes at different loci need to be present in order to cause a particular phenotype.
Example:
C-R- = purple
Chi squared
Statistical test to find out if the difference between observed data and expected data is small enough to be due to chance
Discontinuous variation
Clear categories
Qualitative differences
Different alleles at a single locus have large effects on locus
Different gene loci have different effects on the phenotype
Continuous variation
Quantitative differences
Traits that have continuous variation are controlled by two or more traits
Population
A group of individuals of the same species that can interbred
The Hardy Weinberg principle
To calculate allele frequencies
Assumes: Population is large Mating random No selective advantage for any genotype No mutation, migration or genetic drift
Selection pressure
An environmental factor that confers greater chances of survival to reproductive age on some members of the population
Stabilising selection
A type of natural selection in which allele and genotype frequency within populations stays the same because the organisms are already well adapted to their environment
Genetic drift
The change in allele frequency in a population as some alleles pass to the next generation and some disappear. This causes some phenotypic traits to become rarer or more common
Biological species concept
A group of similar organisms that can interbred and produce fertile offspring
Phylogenetic species concept
A group of organisms that has similar shape, biochemistry, stages of development and behaviour. They also occupy the same ecological niche.
Monophyletic group
One that includes an ancestral organism and all its descendants
Paraphyletic group
Includes the most recent ancestor but not all its descendants.
Reptiles is Paraphyletic as it exclude birds which are descendants of reptiles
Natural selection
The organisms that are best adapted to their environment are more likely to survive. The favourable alleles are passed to their offspring.
Artificial selection
Where humans select the animals with the desirable characteristics. They allows these animals to breed so therefore the offspring have the characteristics wanted.
In cows: Milk yield measured Progeny of bulls tested to see which have high milk yield daughters Artificial insemination Hormones to make many eggs Invitro fertilisation Surrogates
