Inheritence (D3.2) Flashcards
(38 cards)
What is a gene?
A unit of hereditary; a section of DNA that codes for a particular trait
What is an Allele?
An alternate version of a gene
What is a genotype?
The combination of alleles present on chromosomes?
What is a phenotype?
All observable traits of the genotype
What does homozygous mean?
When the alleles of the genotype are the same (DD or dd)
What does heterozygous mean?
When the alleles of the genotype are different (Dd)
How does inheritance occur through the sexual life cycle?
Inheritence occurs as parents pass genes to offspring through gametes, which are haploid and carry one chromosome of each type from both male and female parents, ensuring equal genetic contribution
What does the fusion of male and female gametes result in?
They result in a zygote with a diploid nucleus, containing two chromosomes of each type
How are gametes formed?
Gametes are formed through meiosis.
Where a diploid nucleus divides twice to produce haploid nuclei, allowing the halving chromosome numbers from diploid to haploid
How many copies of each gene do haploids vs diploids carry?
Diploid nuclei contain two copies of each gene while haploid nuclei contain only one
What are the methods of conducting genetic crossing in flowering plants?
- Transferring pollen from the male plant to the female parent using a paintbrush or pollen can be directly dabbed onto the stigma
- Accurate pollination must be ensured (prevent self-pollination). Other pollinating sources must be blocked (using paper bag)
What is pollen germination?
Pollen germination allows male gametes to fuse with female gametes in ovules, forming zygotes that develop into embryos within seeds; parents are referred to as the P generation and the seeds’ offspring as the F1 generation (haha dudududu max verstappen)
What did Gregor Mendel do?
Gregor Mendel’s experiments with pea plants, including crosses between tall and dwarf plants as well as purple and white flowers, established foundational patterns of inheritance by calculating ratios of offspring varieties.
How do alleles lead to genotypes?
Alleles can vary by base sequence and new alleles are generated through mutations. Humans and other diploid organisms inherit two alleles for most gene, one coming from each parent. This results in genotypes such as DD, dd, or Dd
How to homozygous and heterozygous alleles differ?
Homozygous individuals (DD or dd) produce gametes with the same alleles. Heterozygous alleles (Dd) produce gametes with different alleles.
A Dd parent, 50% of gametes with carry the D allele and the other 50% with carry the d allele. This illustrates the concept of allele segregation
What do phenotypic traits result from?
Interactions between an organisms genotype and its environment, some traits are determined exclusively by one or the other
Explain the concept of dominant and recessive genes
One allele, the dominant allele, is expressed (shown) over the other, the recessive allele
When using algebra to express the alleles the dominant allele is usually expressed using a capital letter and the recessive is lowercase
How/why are most alleles of genes produced?
They are mainly produced by mutation of the dominant allele (amino acid sequence changes). This causes the polypeptide to function less efficiently or not at all, this may effect the phenotype. As long as a non-mutated version is present (dominant) the polypeptides can still be produced properly or in enough quantities to function properly
what is phenotype plasticity?
The alteration of gene expression to adapt to their environment, leading to changes in traits.
The adaptation is reversable, involves switching genes on or off rather than changing alleles.
Especially advantageous in a heterogenous environment
How are genetic diseases caused?
Caused by a gene, typically a recessive allele. Disease manifests in individuals with two copies of the recessive allele. Carriers that have one recessive and one dominant allele don’t show symptoms.
Both parents of an affective child must be carriers, usually without knowing. The liklihood of the two carrier parents having a child with the disease is 25%
What is Phenylkentonuria (PKU)?
An example of a recessive allele disease, affected gene is on the chromosome 12.
Results from a mutation in the gene for the enzyme phenylalanine hydroxylase, leading to phenylalanine accumulation.
PKU screening at birth and low-phenylalanine diet can prevent intellectual disability and mental disorders
What is a single-nucleotide polymorphism?
Position in the gene where variations can occur, leading to multiple alleles. Individuals are able to inherit max two alleles in a gene pool
What is evolution?
Changes in the gene pool over time.
What is the S-gene system in apple trees? How many are there? Explain the system
S-gene system in apple tree prevents self-pollination and reduces inbreeding. There are 32 different S-alleles known as S1, S2, S3 etc.
Each diploid apple tree has two copies of the S-gene, with pollen grains containin one alleles.
Pollen is rejected if it shares an S-gene allele with the stigma of the receiving flower. This is the only way that the apple will actually develop
