YR11 - Topic Test - Mendelian Inheritance Flashcards
Genotype
The total set of genes of an organism. The combination of alleles for a trait to be carried by an individual.
Phenotype
An observable trait or character of an organism. The overall appearance of an organism.
Allele
One of the alternative forms of a gene. Most genes have 2 alleles, but more than two alleles are possible.
Dominance
The expression of 1 allele of a gene rather than another allele of the same gene. (covers recessive trait)
Recessive
Relating to a trait or phenotype (encoded by an allele or gene) whose appearance is subordinate to a dominant trait.
Genome
The DNA in one full set of chromosomes present in the nuclei of normal cells of a species.
Eukaryotic
An organism whose cells contain a membrane-bound nucleus and other membrane-bound organelles.
e.g. animals, plants, fungi etc.
Prokaryotic
An organism with cells that do not have a membrane-bound nucleus and lack most organelles.
All prokaryotes are bacteria
Human Genotype Project
A worldwide project started in 1990 to determine the human genome, the precise order of nucleotides within a DNA molecule and the number of genes in one human individual
HGP advantages and ethical considerations
ADVANTAGES
- Predict and prevent diseases changes.
- Improved medicine
- Accurate diagnoses
- Improve forensic science
ETHICAL CONSIDERATIONS
- Informed consent is critical
- Protect patient confidentiality
Structure of Nucleotide
Phosphate
Pentose-Sugar
4 Nitrogen-containing bases
Nucleotide
Nucleotides are the building blocks of nucleic acids such as DNA and RNA.
Complementary base pairings
Adenine - Thymine
Guanine - Cytosine
Hydrogen bonding between complementary DNA strands
Hydrogen bonds are located between the complementary base pairs to help join them together
The effect of heating and cooling on the hydrogen bonds
Heating hydrogen bonds =
When the heat is raised (for instance, as water is boiled), the higher kinetic energy of the water molecules causes the hydrogen bonds to break completely and allows water molecules to escape into the air as gas
Cooling hydrogen bonds =
When water is cooled, the molecules begin to slow down
DNA coiling into chromosomes
In the nucleus of each cell, the DNA molecule is packaged into thread-like structures called chromosomes. Each chromosome is made up of DNA tightly coiled many times around proteins called histones that support its structure.
Nucleosomes help stop the DNA from breaking, but the genes in DNA can still be accessed to make proteins
Coiling DNA
- chromatid vs condensed chromosomes
Chromatid - are short and fat
- like cooked spag (easy to break)
Condensed Chromosome - less likely to break during anaphase of mitosis/meiosis
- like cooked penne (much thicker, not as easy to break)
Karyotypes
A visual depiction of the number, size and shape of chromosomes in an individual.
Monosomy
A condition in which part of all or 1 chromosome of a particular diploid pair is missing in a karyotype.
e.g. turner syndrome
For humans, the term nuclear genome refers to all the genes in
a set of autosomes plus the sex chromosomes.
Trisomy
An abnormality in which a cell has 3 copies of a particular chromosome
e.g. trisomy of chromosome 21 which causes down syndrome in humans
Non-disjunction
the failure of homologous chromosomes or sister chromatids to separate properly during cell division.
Monohybrid cross
A cross between individuals that have different pairs of alleles of a particular gene
e.g. 1 individual might have T and t alleles, the other might have t and t alleles
Monohybrid crosses are used to study the inheritance of 1 characteristic
Dihybrid cross
A cross between pure lineages that exhibit 2 different phenotypes.
e.g. a cross between a pea with dominant phenotypes of yellow seeds and red flowers, and a pea with recessive phenotypes of green seeds and white flowers
Sex-linked inheritance
Inheritance related to genes that occur on the sex chromosomes (X and Y).
e.g. red-green colour blindness, which is caused by a mutation in a gene on the X chromosome
Test cross
A type of backcross in which an individual with the dominant phenotype is crossed with an individual of a recessive phenotype for the character being studied
Multiple alleles
Most genes have 2 alleles (dominant/recessive) e.g. hairline trait
but..
some genes have more than 2 alleles e.g. blood group
Co-dominance
The occurrence of a phenotype in a heterozygous that results from the expression of both alleles
e.g. the AB blood group of humans
Trait
A particular characteristic or feature of an organism
Monogenetic inheritance
Monogenic inheritance refers to the kind of inheritance whereby a trait is determined by the expression of a single gene or allele, not by several genes as in polygenic inheritance.
e.g. hairline, blood type, earlobes
Eukaryotic genome
- DNA in nucleus
- membrane-bound organelles
e.g. mitochondria (tiny bit of dna)
chloroplast (tiny bit of dna)
Eukaryotic genome
- DNA in nucleus
- membrane-bound organelles
e. g. mitochondria (tiny bit of dna)
chloroplast (tiny bit of dna) ONLY in plant cells
Polygenetic inheritance
The inheritance of an observable trait that is determined by many genes.
e.g. height, weight, hair and eye colour etc.
Continuous variation
Polygenetic traits - because there is a greater variation between individuals
Discontinuous variation
Monogenetic traits - because only a few genes control the trait and doesn’t allow much variation
Autosome
Chromosomes that are not sex chromosomes
