ch13 Heredity Flashcards
**HUMAN** male/female :)
What is a gene?
- unit of inheritance
- made of sequence, nucleotides
- part of, DNA molecule
- codes for a single polypeptide.
What are alleles?
- Alternative forms, gene
- occupy same genetic locus
- code, different variants, same polypeptide
- hence give rise, variation, phenotype
Provide an example of alleles in rabbits.
In a certain species of rabbits, one allele codes for black fur (B) and another for brown fur (b).
What is a homologous chromosome?
- pair chromosomes
- one is paternal
- other maternal in origin
- having same shape, length, same genes occupying same genetic loci, same centromere position
Define genotype.
Genetic make-up of an individual.
Define phenotype.
Observable trait of an individual.
What does homozygous mean?
- An individual having identical alleles of a single gene.
- Individual could be homozygous dominant/homozygous recessive
HD -> possess only copies of dominant allele
HR -> possess only copies of reccessive allele
What is the difference between homozygous dominant and homozygous recessive?
HD
possesses only copies of the dominant allele
HR
possesses only copies of the recessive allele.
Define heterozygous.
An individual having different alleles of a single gene.
What is complete dominance?
- allele, complete dominance, other alleles
- suppresses effect, recessive allele
- dominant allele, fully expressed, manifested, phenotype, homozygous
dominant, heterozygous individuals.
What is co-dominance?
- allele, codominant w/ another allele of same gene
- equally expressed, manifested -> phenotype, heterozygote.
Define recessive allele.
- allele, suppressed by effects, dominant alleles
- only expressed, phenotype homozygous recessive individuals.
Why do observed ratios often differ from expected ratios?
- Expected ratios, calculated probabilities, based off theoretical model
- Observed ratios -> random chance
- as sample size increases, observed ratios become closer, expected ratios.
Explain the inheritance of ABO blood group phenotypes.
ABO blood types,
controlled 1 gene, 3 alleles
- Ia, Ib, Io,
- co-dominance, multiple (>2) alleles.
- Ia Ib codominant
- Io recessive to Ia Ib
What is the chromosomal composition of human females?
Human females
- 22 pairs autosomes,
- 1 pair sex chromosomes
- 2 X chromosomes
ovum what chromosomes
ovum produced, female
all ovum, only contain X chromosome
What is the chromosomal composition of human males?
Human males
- 22 pairs autosomes,
- 1 pair sex chromosomes
- 1 X 1 Y chromosome
all sperm what chromosomes
sperm produced, male
half sperm cells, X chromosome,
other half sperm cells, Y chromosome,
how is human female made from sperm, egg
- sperm cell containing X chromosome, fertilise ovum
- offspring possess 2 X chromosomes
- female
how is human male made from sperm, egg
- sperm cell containing Y chromosome, fertilise ovum
- offspring possess 1 X 1Y chromosome
- male
Define mutation.
random change, nucleotide sequence of gene, or number of chromosomes
explain mutation causing Type 1 Diabetes Mellitus
- mutation results, random change, nucleotide sequence, insulin gene
- mutated gene, transcription, mRNA molecule, corresponding change, nucleotide sequence
- mRNA undergoes translation, ribosomes, produce polypeptide, incorrect amino acid sequence, fold, dysfunctional insulin molecule
- liver cells, dosent recognise dysfunctional insulin molecule,
- does not absorb glucose or convert glucose -> glycogen,
- even when excess glucose, bloodstream
- excess glucose, excreted -> urine, Type 1 Diabetes Mellitus
Down Syndrome cause, what characteristics
- change, chromosome number;
- Down Syndrome, trisomy chromosome 21.
- Stunted growth, mental impairment
What are two factors that may increase the rate of mutation?
- Ionising radiation
- Chemical mutagens
Examples include X-ray and tar.
What type of ionising radiation is mentioned as a factor increasing mutation rates?
Ultraviolet radiation
Ultraviolet radiation is a form of ionising radiation.
Name a chemical mutagen that may increase mutation rates.
Formaldehyde
Formaldehyde is known for its mutagenic properties.
What is the role of natural selection in evolution?
- mechanism, gradual change
- inheritable characteristics
- population
- over time
It involves the survival and reproduction of individuals with advantageous traits.
Selection Pressure
- Random gene mutation, sexual reproduction, genetic variation
(specific phenotype) among (individuals), population - (factor) exerts, selection pressure,
(individuals), (advantaged phenotype), better adapted, (explain adaptation, environment) - (individuals), (disadvantaged
phenotype) dies off, (factor). - (advantaged phenotype) (individuals) SURVIVE LONGER, reproduce more offspring,
INHERIT allele, (advantaged phenotype). - proportion, population, ALLELE (advantaged phenotype)
increase gradually, many GENERATIONS, evolution, population, (advantaged phenotype).
The specified phenotype can be any trait being studied.
Define artificial selection.
The process whereby animal or plant breeders select organisms with desirable characteristics to reproduce.
This results in the passing on of favorable alleles to offspring.
Give an example of artificial selection.
Pollinate flowers belonging to soyabeans with high oil content with each other.
This example shows how breeders can enhance specific traits in crops.
Another example of artificial selection involves breeding cattle. What is the goal?
To produce large amounts of milk by breeding closely related individuals.
This practice aims to enhance milk production traits in cattle.
selection pressures
evolution
- overpopulation
- changing environment
- resource competition
- predators
continuous variation characteristics
- intermediate forms, gradation, one extreme, another
- affected by env.
- controlled, many genes
- show additive effect
additive effect
means (Gene 1 lower backbone height medium) + (Gene 2 higher backbone height tall) = relatively tall individual
continuous variation example
height
skin colour
discontinuous variation
- phenotypes distinct, one another, easily sorted, categories
- not affected by env
- controlled by 1, few genes
- does not show additive effect
