Mendelian Genetics and Inheritance Flashcards Preview

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Flashcards in Mendelian Genetics and Inheritance Deck (47):
1

what is tooth agenesis?

  • failure of a tooth to form
  • the most common heritable disorder in humans

2

tooth agenesis affects ___% of the population worldwide, if ___ are excluded

  • 4-7%
  • 3rd molars

3

of the population affected by tooth agenesis, ___% are missing 3 or more teeth

1%

4

if 3rd molars are included in tooth agenesis stats, ___% of the population is considered to be affected by tooth agenesis

20%

5

mendelian genetics is a model of ___ first described by gregor mendel

inheritance

6

what is a phenotype?

a physical trait

7

mendel cross bred plants with various phenotypes and recorded the ratio of offspring across generations.  this led him to formulate his ___

3 laws of inheritance

8

name the 3 laws of inheritance

  1. the law of segregation
  2. the law of independent assortment
  3. the law of dominance

9

what is the law of segregation?

  • factors for each trait segregate, such that each gamete carries only one factor for each trait

10

what is the law of independent assortment?

each factor that segregates does so independently

11

what is the law of dominance?

some factors are dominant and some are recessive.  the dominant trait will always be expressed when present

12

what are mendel's heritable factors referred to as?

alleles

13

what are alleles?

  • the different forms of a gene
  • for example, flower color

14

law of segregation

there are ___ copies of each allele, and further, they are ___

  • two
  • separated
  • consider meiosis: diploid (2n) cells become haploid (1n)

15

the law of segregation

one copy of a ___ comes from one parent, and the other copy comes from the second parent

gene (allele)

16

law of independent assortment

mendel concluded that not only did copies of a single allele separate, but that alleles for different traits separated ___ of one another

  • independently
  • for example: flower color and seed color both have an allele with 2 copies.  both of these alleles will be distributed according to the law of segregation, but will do so independently of one another.

17

law of independent assortment

the number of ___ depends on the number of ___ we are considering

  • combinations
  • alleles

18

law of dominance

mendel observed that each trait has a ___ and ___ form

dominant and recessive

19

law of dominance

a ___ allele will always be expressed when present

dominant

20

law of dominance

what must occur in order for a recessive allele to be expressed?

both copies of the allele must be recessive

in other words, the dominant allele must not be present

21

describe the difference between homozygous and heterozygous

  • homozygous: organisms can be either homozygous dominant or homozygous recessive, and therefore will only pass along the allele they express
    • ex. AA or aa
  • heterozygous: organisms will always express the dominant allele, while carrying (and passing) the recessive allele
    • ex. Aa

22

does dominance imply normality?

no; it is simply preferred expression

23

dominance is not ___, but relative to an allele that is also present

inherent

24

T or F:

dominant traits are always the most common in a population

false:

they can actually be rare

25

what is a genotype?

alleles that are present

vs. phenotype, which are the traits that are expressed

26

in mendel's observations from his second generation crosses, he observed a phenotypic ratio of ___:___

3 dominant : 1 recessive

27

in the first generation, assuming a cross between two "true breeding" or homozygous organisms, we will always get what? what laws of inheritance do we see here?

  • heterozygotes, expressing the dominant allele
  • 1st and 3rd laws

28

once we start crossing the results of the F1 generation, are we dealing with true breeding parents?

no

29

breeding of what generation yields mendel's 3:1 phenotypic ratio?

breeding of the F1 generation, so the F2 generation shows the 3:1 phenotypic ratio

30

what is the phenotypic composition of the F2 generation when parents of the F1 generation are true breeders? which laws of inheritance are seen?

  • 50% true breeding (homozygous) and 50% heterozygous organisms
  • 1st and 3rd laws
  • this will be the result regardless of the offspring chosen from the F1 generation

31

the fact that recessive genes can be carried allows the ___ of certain genes, even if they aren't favored when expressed.

  • preservation
  • it will eventually allow a recessive phenotype to resurface should environmental selection pressure change

32

___ and ___ allows a species to resist extinction

genetic variability and selection

33

any patterns of inheritance which do not strictly follow the three laws of inheritance are said to be ___

non-mendelian

34

what are two examples of co-dominance?

  1. more than two possible alleles, even though each individual only carries two copies
  2. situations where more than one of these possible alleles are dominant, and can be expressed as a distinct co-dominant phenotype

35

blood groups are an example of what?

co-dominance

*non-mendelian genetics

36

what is incomplete dominance?

snapdragon example

  • if the alleles for white flowers (recessive) and red flowers (dominant) are both present, you end up with a weaker expression of red, resulting in pink flowers
  • there is no allele for pink flowers, but it is a possible phenotype when both red and white alleles are present

37

what is mosaicism?

  • when different cells in the body have different genotypes, and thus express different phenotypes
  • calico cats are an exmaple

38

sex-linked dominance

a __-linked trait would only be passed on to male offspring, and is relatively small so it contains ___ genes.

  • Y
  • fewer

39

sex-linked dominance

for __-linked dominant traits, inheritance depends on the relative genotypes of the parents

X

40

sex-linked dominance

a father with a dominant X trait will pass it to his ___ but not his ___.  a mother would distribute ___% of all offspring depending on her genotype.

  • daughters
  • sons
  • 50-100%

41

sex-linked dominance

which traits will predominate in males? which females will be affected?

  • X-linked recessive
  • females who are homozygous are affected

42

sex-linked dominance

___ in females can result in limited expression of an X-linked recessive trait

X-inactivation

43

what is extranuclear inheritance? what is an example?

  • factors passed form the cytoplasm
  • ex. mitochondrial DNA all comes from the ova

44

___ is a recombination event where DNA sequence from one homologous chromosome can replace a sequence on its counterpart.

gene conversion

45

gene conversion can interfere with ___

mendelian ratios

46

describe infectious heredity

when integrated traits introduced by a virus are passed along the germ line; this is typically passed directly along from one parent

47

T or F:

traits result as equal contributions from parent organisms

not always