Inheritance Flashcards
How does sexual reproduction cause variation?
gametes fuse and one of each pair of alleles comes from each parent
How many pairs of chromosomes are in human body cells and how do they determine sex?
23 pairs of chromosomes
in females the sex of chromosomes are the same (XX); in males the sex chromosomes are different (XY)
What are characteristics controlled by?
some characteristics are controlled by a single gene
each gene may have different forms called alleles
When is a allele dominant?
an allele that controls the development of a characteristic when it is present on only one of the chromosomes is a dominant allele
When is a allele recessive?
an allele that controls the development of characteristics only if the dominant allele is not present is a recessive allele
What are chromosomes made from?
large molecules of DNA which has a double helix structure
What are genes made from and what is there function?
a gene is a small section of DNA
each gene codes for a particular combination of amino acids, which makes a specific protein
What causes polydactyly?
caused by a dominant allele of a gene
therefore it can be passed on by only one parent who has the disorder
A - polydactyly allele
a - normal allele
A a
a Aa aa
a Aa aa
Aa has polydactyly
What causes cystic fibrosis?
it is a disorder of cell membranes
recessive so it must be inherited from both parents
parents may be carriers without having the disorder
How can genetic disorder be prevented?
embryos can be screened for the alleles that cause the genetic disorders
What did Mendel discover?
studied the characteristics of different pea plants
he found when he bred red-flowered plants with white-flowered plants, all the offspring produced red flowers, but some had white
this is because the allele for red flowers is dominant
