Heredity Flashcards
(31 cards)
Define genetics.
The study of heredity, which studies inherited traits
List some examples of inherited traits.
- height
- eyes
- hair
- shape of nose
List some examples of acquired traits.
- weight
- tan
- accent
Define a phenotype.
A visible/measurable trait that is passed on
Define a genotype.
Traits controlled by genes and found in every cell in the body
Discuss the connection between chromosomes and genes.
- each chromosome can have one million or more genes, one for each trait
- the more important genes are closer to the center
What is the difference between homozygous and heterozygous genotypes?
Homozygous are two of the same traits, or a pure individual; heterozygous are two different traits, one being dominant, called a “hybrid individual”
Give the scientific terms for different generations.
Parents: P generation
Parents’ offspring: F generation
Offsprings’ offspring: F2 generation, etc.
Who was Gregor Mendel?
An Austrian monk who studied math and science the mid 1800s; known as the “father of genetics” and investigated genetics at the organism level by studying pea plants
What are some of Gregor Mendel’s discoveries?
- offspring traits were never intermediate (a mix of both), and only resembled one parent
- true breeding: all the same traits in all offspring
- not true breeding: some offspring have different traits
What is the theory of inheritance?
- offspring inherit alleles from parents, which code for traits
- each offspring has two alleles for each trait
- the position on the chromosome where the allele is located is called loci, or a locus
What are the two laws of inheritance?
1) law of segregation
- each individual has two alleles for each trait
- each gamete has one allele
- alleles of paretns combine during fertilization in different but predictable combinations
- the phenotype doesn’t blend, but is either on or the other
2) law of individual assortment of alleles
- alleles of different traits pass to offspring independently
- alleles controlling different genes are randomly distributed to gametes
- e.g. the colour of a pea pod does not affect the texture
- except for alleles located on the same chromosome, which are inherited together (e.g. red hair and freckles)
Define complete dominant inheritance.
When a heterozygous phenotype is intermediate between two phenotypes; the traits blend (e.g. red flower and white flower becomes a pink flower)
Define codominant inheritance.
Two dominant traits are both expressed in offspring (e.g. white flower and purple flower become a white and purple striped flower)
Discuss multiple alleles.
Due to mutations or other chromosomal changes, an allele may alter its form and express a slightly different phenotype; a new allele is created, and two or more alleles exist for a specific trait (e.g. humans have three different blood types, A, B, and O)
Define an autosome.
All chromosomes (pairs 1-22) except the sex chromosomes, which are the twenty-third pair
What are sex-linked genes?
Traits located on the X or Y chromosomes; because the X chromosome is much larger, more traits are carried on it than on Y
Explain why men are more likely to get X-chromosome traits.
Because there are more traits on the X chromosome than the Y; therefore, because men only have one X chromosome, those traits are determined by only one allele
How many base pairs do X and Y chromosomes have?
X: 153 million
Y: 50 million
What are some X-related genetic conditions?
- Hemophilia (blood can’t clot)
- colour blindness
- Juvenile muscular dystrophy
Define polygenetic inheritance.
A trait controlled by two or more sets of alleles, which may be on different chromosomes; each dominant allele has a quantitative affect on the phenotype, and results are cumulative (e.g. eye colour can be light to dark brown)
Discuss the relationship between genes and the environment.
The environment of an organism affects the phenotype; some traits make the organism more successful than others (e.g. colours that camouflage)
Define genetic mutations and list the two types.
Changes in genetic information that become part of the individual’s genotype
- Somatic: passed to the descendants of cells within the organism, but not passed to offspring (e.g. some cancers)
- Reproductive: passed on to gametes, then on to offspring
Define mutagens and list some examples.
Environmental factors that cause genetic mutations
- very high temperatures
- viruses
- chemicals
- radiation
