Genetics Flashcards
(14 cards)
DNA recap
fundamental unit in a double-helix structure
- packed into chromosomes
- 23 pairs, 22 are autosomes, the rest is a sex chromosome
- genes contain the instructions to produce a particular protein and by themselves and they don’t do anything, they only produce the protein when they are expressed (which is why we share 99% with chimpanzees but look nothing like them (they are expressed differently))
zygote recap
formed from a single cell
allele recap
different genes from mother and father
homozygous - when you get some allele from both parents
heterozygous - the opposite
genotype phenotype recap
genotype - inherited
phenotype - visual characteristics when it interacts with the environment
- may not be seen depending on the environment that it is interacted with
Dominant VS Recessive Genes
- Dominant genes express the phenotype even in the heterozygous form (BB or Bb both produce brown eyes, overpowered by B)
- Recessive genes only express the phenotype when it is homozygous
Disorders Caused by Dominant Genes
Huntingtons
- Rare neurodegenerative disease, onset around 40
- Affects muscle coordination (huntington’s chorea)
- Repetitive movements, lack of control over muscles
Phenylketonuria (PKU)’
- Inability to metabolise phenylalanine
- Cognitive deficits, seizures, shortened lifespan
- ¼ likelihood for child
- Some parents won’t know they have the gene
as it goes generations back
Down Syndrome as a Developmental DIsorder Caused by Genetic Mutations
Downs syndrome
- Extra copy of chromosome 21
- 1 in 1000
60 year life expectancy
= Cognitive and learning delays
- High comorbidity with alzheimers
Fragile X as a developmental disorder caused by genetic mutations
- Lengthening of the FMR1 gene on the x chromosome
- 1 in 3600 boys
- 1 in 4000-6000 girls
- Normal life expectancy
- Commonly meet criteria for autism
- physical features
- Developmental delays in language, social interactions, behaviour
Advocating a Gene x Environment Interaction
genes do not do anything until they are expressed, therefore even the most basic gene processes are influenced by the environment
Turtles and Sex Determination and justifying a Gene x Environment Interaction
- Whether the eggs turn out male or female depends on the temperature of the nest at the point that they are laid and incubated
- 29.2 degrees is the threshold for males and females
- At 26 degrees all the eggs will be male
- At 31 degrees all the eggs will be female
- Totally environmental
Sex Characteristics are Largely Genetic for Humans
Male parent will decide the gender through specific pair chromosomes
- XX in female, XY in male
Human Sex Characteristics determined by the environment to some extent
- For the first 7 weeks of gestation, XX and XY look the same
- Mullerian ducts and wolfian ducts both as a precursors to female and male organs
- At 7-8 weeks a gene on the Y chromosome makes the testes develop
- Testosterone makes the system develop into male genitalia
- In the absence of testosterone the mullerian system develops into female genitalia and the wolfian system is absorbed
Androgen Insensitivity Syndrome (AIS)
- XY genetically, but body does not detect and respond to male hormones
- Disruption to sex determination
- Detected during puberty, when it is abnormally delayed, test to find that they are naturally male
Congenital Adrenal Hyperplasia (CAH)
- Exposed to excessive levels of male hormones prenatally
- Presentation of the male genitalia despite having XY chromosome
