what is a gamete?
a gamete is a sex cell( sperm or egg)
what is a gene
a section of dna that can ( but not always ) code for a protein
What is a chromosome
tightly packaged DNA around histone proteins
what is an alllele
different versions of the same gene
what is a dominant allele
a version of a gene where only one copy is needed for it to be expressed
What is a recessive allele
a version of a gene where two copies are needed for it to be expressed
What is meant when an organism is homozygous
when an organism has two copies of the same allele ( two recessive or two dominant)
What is meant when an organism is heterozygous
when an organism has two different versions of the same gene ( one recessive and one dominant)
What is the genotype
the genes present for a trait
what is the phenotype
the visible characteristic
what is the genome
all of the genes present in an organism
what is discontinuous variation
variation that produces distinct categories (e.g. eye colour or blood groups)
what is continuous variation
variation that cannot be placed into distinct categories and instead produces a spectrum (e.g. height, weight)
What causes variation
mutations in the genetic code
Describe how a mutation in a coding DNA sequence could be detrimental
the mutation may change the sequence of amino acids in the protein which will change its structure
this may affect the protein, particularly in specific molecules like enzymes and anitbodies
what may happen if there is a mutation in non coding dna
it may stop transcription and alter the expression of genes
give one advantage and one disadvantage of sexual reproduction
advantage - it introduces variation
disadvantage - it it slower and produces a limited amount of offspring
give one advantage and one disadvantage of asexual reproduction
advantage - it produces lots of offspring quickly
disadvantage- it does snot introduce variation and so all offspring are susceptible to the same environmental pressures as the parents.
what is the difference between diploid and haploid cells
haploid cells have half the amount of genetic information( 23 chromosomes instead of 46) as diploid cells
haploid cells are germ cells
diploid cells are body cellss
what type of cells does meiosis produce
haploid germ cells (sperm and egg cells)
how are dominant alleles represented in a Punnett square
they are represented using uppercase letters
How are recessive allelese represented in a Punnett square
they use the lowercase version of the same letter as the dominant allele
give 3 important findings of gregor mendel
organisms inherit hereditary units from their parents
offspring receive units from both parents and so share traits with both parents
traits can be passed on but not visible
what discovery lead to people accepting Mendel’s ideas
the discovery of the gene
