D3.2: Inheritance Flashcards
(21 cards)
What is inheritance?
Inheritance refers to a trait passed from parent to offspring during reproductions
DNA -> molecules of inheritance for all living organisms
What are haploids and diploids?
Haploids:
One chromosome of each type
Ex: gamete
Diploids:
Two chromosomes of each type
Ex: zygote
What are gametes?
Sex cells of an organism
One copy of each chromosome -> haploids
In humans: sperm and egg (ovum) cells with 23 single chromosomes
- egg is larger -> contains food for growing embryo
- sperm many mitochondria -> release energy for motion
Fuse during fertilization -> zygote -> 46 chromosomes
What is sexual production?
Process involving the fusion of nuclei of two gametes (sex cells) to form a zygote (fertilized egg cell) and the production of offspring that are GENETICALLY DIFFERENT FROM EACH OTHER
Results in diploid zygote:
-> two copy of each chromosome
-> two alleles of each gene
What does it mean when a genotype is homozygous or heterozygous?
Homozygous:
Both alleles for a particular gene are the same
Heterozygous:
The two alleles for a particular gene are different
How did people think inheritance worked before Mendel?
Idea of blending inheritance
Eg: white and purple flower -> light purple intermediate ‘child’
What is cross pollination? How do you preform it artificially?
Cross pollination:
One plant fertilizes another plant of the same species
Transfer pollen (male gamete) from one plant to the reproductive parts (ovary) of another
Used by Mendel and his pea plants to investigate height/color of flower/smoothness -> eliminates uncertainty from his data
What were the results of Mendel’s crosses?
Establish pea plant population with two different features
Breed until they always produced offspring identical to the parent
Crosses plants with each other -> observe inherited traits
F1: all plants were identical in shape to one of the parents
-> directly contradict blending inheritance
-> conclusions: dominant and recessive
F2: wondered what happened to recessive characteristic -> assumed ‘inherited unit’ produced each phenotype -> did recessive disappear or masked? -> self fertilize F1 generation that displayed dominant trait
-> recessive traits appear
Conclusion:
Phenotypes were determined by a combination of ‘discrete heritable units’ (alleles)
Called particulate inheritance hypothesis
What is a monohybrid trait?
One that is controlled by one gene
What things are needed when doing a punnets grid?
Gene
Alleles
Parent genotypes
Unique gametes from each parent
Draw Punnett square
List genotype
List phenotype
Ratio of phenotype
What is a gene?
A short length of DNA found on a chromosome that codes for a particular characteristic (code for the production of a specific protein)
What are alleles?
A different versions of the same gene
Code for the same type of protein
Have difference in a sample base/large sections
New alleles generated by mutation (SNPs)
What is the genotype of a person?
The combination of alleles that an individual organism inherits
Can be homo or heterozygous
What is the phenotype of a person?
The observable traits or characteristics of an individual
Included by both genes and environment
Examples:
Genes only: blood group, PKU disease, haemophilia
Environment only: scars, body art, language spoken
Both: height, type II diabetes, tanning, coronary heart disease
What is a dominant allele?
Alleles that will produce a certain phenotype and will always be expressed if present
Cause:
Dominant allele typically encodes for a functioning protein -> one copy of allele all that is needed in order to make enough of the protein coded for by that gene
What is a recessive allele?
Alleles that will produce a certain phenotype that will only be expressed if the genotype is homozygous
Causes:
Recessive allele codes for a nonfunctioning protein
Recessive allele is the normal one and dominant is the mutated version -> need two good for normal function
What is phenotype plasticity?
The idea that although genotype remains fixed through an organisms lifetime the way the phenotype is expressed can vary over time
Organisms internal/external environment can influence gene expression
- level of regulatory proteins or transcription factors affected by light, chemicals, drugs, hormones, temperature
What is a genetic disease?
An illness caused in whole or in part by a change in the DNA sequence away from the normal sequence
-> Most are caused by recessive gene
Can be:
Dominant: if person has one dominant -> develop disease (Huntington’s disease)
Recessive: person no dominant -> develop disease (cystic fibrosis)
Co-dominant: heterozygotes have different phenotypes than individuals with two copies of either allele (sickle cell disease)
Autosomal: gene located on autosome -> males and females equally affected
Sex-linked: gene located on a sex chromosome -> different pattern of inheritance in males and females (haemophilia)
Example of genetic disease (autosomal recessive): PKU
Phenylketonuria
Mutation in PAH gene on chromosome 12
Normal allele (dominant):
Code for functioning phenylalanine hydroxylase
- converts AA phenylalanine -> AA tyrosine
Disease allele (recessive):
Mutation cause production of non-functioning phenylalanine hydroxylase
Phenylalanine not processed effectively -> accumulates + tyrosine deficient -> high concentration phenylalanine neurotoxic -> brain damage (mental disorders, seizures, etc.)
In many counties babies are tested for several genetic conditions upon birth -> PKU included (PKU first conditions for widespread newborn testing)
Diet must have little/no phenylalanine -> limit amount of protein and supplements taken
If children are placed on diet upon birth -> grow normally, no symptom or health problems
What are SNPs?
