IB Biology HL: Inheritance - D3.2

nondisjunction

during meiosis 2, DNA fails to separate correctly into equal sections. Will cause genetic diseases

allele

variation of a same gene

monohydrid inheritance

crossing of hogemozygous dominant and homozygous recessive, in generation 1 phenotype will be 100% dominant, genotype 100% heterozygous, and generation 2 has phenotype 75% dominant, 25% recessive, genotype= 25% homo dominant, 25% homo recessive , 50% hetero

codominant allele

pairs of alleles that both affect the phenotype when present in a heterozygote

locus/ loci (plural)

the particular position on homologous chromosomes of a gene

test cross

testing a suspected heterozygote by crossing it with a known homozygous recessive

phenotypic plasticity

The capacity to develop traits suited to the environment experienced by an organism, by varying patters of gene expression. But same genotype, just different expression

example: artic fox

blood groups

presence or abscence of a agglutinogen or b agglutinogen

presence or absence ofRh

universal donor

blood group O -

universal recipient

blood group AB+

Phenylketonuria

a recessive genetic condition caused by mutation in an autosomal gene that codes for the enzyme phenylalanine hydroxylase, needed to convert phenylalanine to tyrosine. 

Phenylalanine builds up:

• production of melanin is severely reduced

• serotonin and dopamine production are severely affected 

• Neurological symptoms include seizures, abnormal muscle movements, tight muscles, involuntary movements and tremors. 

• Left untreated can lead to severe brain damage. 

• Treatment consists of diet severely restricting the intake of foods with phenylalanine 

incomplete dominance

where a dominant alleles does not completly mask the effects of a recessive allele, resulting in heterozygotes having an intermediate phenotype.

incomplete dominance example

mirabilis jalapa. Pink flower(partially domminant) and white flower(recessive) cause soft pink flower.

in diagrams, choose a third party letter to make uppercase (C for colour), put in hypertext the feature you want to highlight, and treat normally

gonad

organ in foetus which produces gametes

creation of males

• foetuses are the same until 7 weeks,

• on Y chromosome is prime male-determining gene

• codes for testis-determining factor

• functions as molecular switch, which initiates testosterone production

• in embryonic gonad tissue, inhibits development of female genitalia, and causes the development of testes, scrotum, and penis

• no Y chromosome ? embryonic gonad tissue forms an ovary, and later from hormones in the ovary cause further development

sex linkage

Sex linkage refers to the inheritance of genes located on a sex chromosome (usually the X chromosome) 

genetic basis of continuous variation

• caused by interactions between genetics and environment

• phenotype= genetics + environement

• skin colour is ib example

polygenes

a large number of genes which ave a combined effect on the phenotype

comparison between continuous vs discontinous variation

• features can be measured across a complete range, vs distinct classes and categories (quantitative vs discrete data)

• many loci for continuous, while for discontinuous one or very few

• many intermediate phenotypes vs feature either present or absent

• for continuous variable environment is a big factor, while for discontinuous, little to no influence

unlinked genes

genes that an organism carries on a separate chromosomes

example of dominant, automosal disease

huntington’s

bivalent

two homologous chromosomes, bound by chiasma, during meiosis

segregation of chromosomes

which pole of the cell a homologous chromosome gets pulled in anaphase 1, determining which combination of alleles end up in meiosis 2

Mendel’s law of independent assortment

alleles of different genes are inherited independently of one another

linked genes

genes which tend to be inherited together as they on the same chromosome close together

dihybrid crosses

shows how two unlinked genes transfer across generations → do one to check you remember

dihydric heterozygous crosses for unliked genes ratios

9:3:3:1

dihydric one parents heterozygous and other homozygous recessive crosses for unliked genes ratios

1:1:1:1

mendel’s second law

a pair of traits segregates independently of another pair during meiosis when the sperm and eggg are created during meiosis.

not universally true, for example linked genes do not follow expected ratios

sex-linked genes

genes on the X or Y sex chromosomes

autosomal genes

genes that are not located on X or Y chromosomes, affect individuals regardless of sex

notation of linked genes

linking them with lines, representing the homologous chromosomes

used when dihydric fails as independent assumption isn’t true

recombinant offspring

children who have parents with specific linked genes who do not have the expected traits; that is because of crossing over which occurs during meiosis

organism used to investigate genes

fruit flies