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Flashcards in Genetics Deck (86)
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1

Genes

hereditary units of DNA transmitted from one generation to another; code for proteins

2

Locus

the specific location of a gene on a chromosome

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Alleles

different versions of a gene; humans have 2 alleles for each autosomal gene

4

Chromosomes

structure composed of genes located in nucleus of a cell

5

How do you distinguish chromosomes from each other?

Overall length and position of the centromere(divides chromosome into 2 arms: short:p, long:q)

6

Homologous chromosomes

have the same genes at the same loci, one maternal and one paternal

7

Genome

the genetic information contained in the cells, on the chromosomes, for a particular species

8

How many chromosomes in the nucleus of a human somatic cell?

46(23 pairs)

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Mutations

A change in some part of the DNA code
-Spontaneous/Induced: exposure to mutagenic chemical or radiation
-varying effects based on location
-net result can be a physical change or other trait

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Autosome

any chromosome that is not a sex chromosome (humans have 22 pairs of autosomes)

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Allosome

Sex chromosome pair, humans have one

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Somatic cell

contain one homologous set of chromosomes from mother/Father
-22 pairs in humans

13

Haploid vs Diploid

Haploid(n): # of chromosomes in sex cells/gametes(n=23)
Diploid(2n):# of total chromosomes in somatic cells(2n=46)

14

What are the parts of the human chromosome?

-short arm= p
-long arm= q
-chromosomes numbered consecutively by length: longest first.

15

Sex Chromosomes

Human males have one morphologically dissimilar pair of chromosomes – the sex chromosomes
Heteromorphic (contrast with homologues)
Labeled X and Y
Genetic factors on the Y determine maleness
Human females have two morphologically similar X’s

16

karyotype

picture of a person’s chromosomes

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Mitosis

-The process by which all somatic cells become descendants of one original cell
-One exact copy of each chromosome is made and distributed through the division of original cell into two daughter cells

18

Meiosis

-The process by which gamete cells are produced (egg and sperm)
-Resulting gametes have 23 new chromosomes (one member of each of the pairs), with new combos of the original maternal and paternal copies
-Occurs only in specialized germ cells of gonads
-2 consecutive cell divisions producing cells with half the original chromosome number
diploid 2n--->haploid n

19

Gametogenesis

-Diploid primordial cells in testes become spermatogonia
-4 sperm cells (spermatozoa), each is haploid (n)


-Diploid primordial cells in ovaries become
oogonia
-1 haploid ovum (n), and polar bodies which degenerate

20

Genotype

all of the alleles of an organism
-Homozygous – contains the same alleles at a single locus
-Heterozygous – contains 2 different alleles at a single locus

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Phenotype

a measurable trait an organism has
-Result of gene products that interact in a given environment

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Dominant allele

phenotype can be seen in both the heterozygote and homozygote
-Carrier – heterozygous individual with a recessive allele that’s hidden from phenotypic view by the dominant, normal allele

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Recessive allele

produces this phenotype only when its paired allele is identical

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Single gene disorders (Mendelian disorders)

Classified by whether they are
-Autosomal or x-linked
-Dominant or recessive pattern

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Punnett square

illustrates a monofactorial cross – a mating in which a single gene is analyzed
-This type demonstrates Mendel’s principle of segregation: one parent has 2 copies of a gene for each trait, but transmits only one via a gamete

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Albinism

AA(homozygous dominant)=Pigmented
Aa(heterozygous)=Pigmented
aa(homozygous recessive)=Albino

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Codominance

when two alleles for a trait are equally expressed (example: AB blood type)
-When alleles lack complete dominant and recessive relationships and are both observed phenotypically (expressed at the same time)
-Seen in chickens and cattle as well

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Incomplete dominance

heterozygotes have phenotypes that have both alleles visible as a blend (one allele isn’t expressed over the other)
-Makes a third phenotype that’s a blending of the two
-Human examples: wavy hair – it’s a blend that’s seen when a person with straight hair has a child with a person with curly hair; skin color

29

Penetrance

the probability that individuals in a population who have a particular gene combination will show the condition
Example: if a mutation causing diabetes has 95% penetrance, 95% of people with the mutation combo will develop diabetes

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Genetic marker

Sequence of DNA with a known location on a chromosome