topic 14 - inheritance Flashcards
what is a genome
The entirety of an organism’s DNA
what is a gene
a section of DNA which codes for the formation of proteins controlling a specific trait of an organism
what are chromosomes
a thread of DNA, made up of genes
how many chromosomes do humans have
23 pairs, so 46 chromosomes
what is DNA
genetic material found in the nucleus of a cell. it is a polymer made up of two strands coiled around to make a double helix
what are alleles
an alternative form of a gene
what is a dominant allele
a gene that always shows up in phenotype, even in a heterozygous state
what is a phenotype
The visible characteristics of an organism
what is a genotype
the genetic makeup of an organism
what is a recessive allele
A recessive allele needs to be inherited from both parents for the characteristic to show up in the phenotype.
what does homozygous mean
having a pair of same alleles e.g. AA or aa
what does heterozygous mean
having a pair of dissimilar alleles e.g. Aa
what is a gamete
sex cells
what is polygenic inheritance
Characteristics that are controlled by more than one gene. they have phenotypes that can show a wide range of combinations of features
what is monohybrid inheritance
the inheritance of characteristics controlled by a single gene
how to construct a Punnett Square
- Determine the parental genotypes
- Split the alleles for each parent and add them to the Punnett square around the outside
- Fill in the middle four squares of the Punnett square to work out the possible genetic combinations in the offspring
what are family pedigrees
diagrams that are usually used to trace the pattern of inheritance of a specific characteristic (usually a disease) through generations of a family
how to interpret family pedigrees
- Males are indicated by the square shape and females are represented by circles
- Affected individuals are red and unaffected are blue
- Horizontal lines between males and females show that they have produced children (which are shown underneath each couple)
how is sex determined
- Sex is determined by an entire chromosome pair
- Females have the sex chromosomes XX
- Males have the sex chromosomes XY
what is mitosis
nuclear division giving rise to genetically identical cells
4 things mitosis is used for
- growth
- repair of damaged tissues
- replacement of cells
- asexual reproduction
what is a diploid nucleus
a nucleus containing 23 pairs of chromosomes e.g. general body cells
what is a haploid nucleus
a nucleus containing 23 unpaired chromosomes e.g. sex cells
process of mitosis
- The parent cell duplicates itself
- the replica splits into 2 daughter cells that are genetically identical, with no genetic variation
what is meiosis
nuclear division that gives rise to cells that are genetically different
process of meiosis
- parent cell duplicates itself
- the replica splits into 2 daughter cells
- the 2 daughter cells produce 4 daughter cells which are genetically different, leading to genetic variation
differences between mitosis and meiosis
- mitosis produces 2 daughter cells, meiosis produces 4 daughter cells
- mitosis produces diploid daughter cells, meiosis produces haploid daughter cells
- in mitosis, 1 cell division occurs, in meiosis, 2 cell divisions occur
what is the idea of random fertilisation
During fertilisation, any male gamete can fuse with any female gamete to form a zygote. This random fusion of gametes at fertilisation creates genetic variation between zygotes as each will have a unique combination of alleles
what is the diploid number of chromosomes in a person
46
what is the haploid number of chromosomes in a person
23
what is variation
differences between individuals of the same species
what is environmental variation
when characteristics are solely focused on environmental factors e.g. climate, diet.
what is genetic variation
when characteristics are solely influenced by genetics e.g. parent genes
2 examples of environmental variation
- tattoos
- piercings
2 examples of genetic variation
- eye colour
- blood group
what are mutation
rare, random changes that occur in the sequence of DNA bases in a gene or a chromosome
