Biology Chapter 7 Flashcards
Any of the alternative forms of a gene
alleles
Gene expression is often related to whether a gene is located on an ______ or a ____ ________
autosome, sex chromosome
One of the factors that affect phenotype is which _________ a gene is located on
chromosome
Why can the probability of autosomal disorders be predicted?
Each human autosome has 2 homologous chromosomes (X X), with one gene on each, M & F, that each influence phenotype
Disorders can be caused by ______ or ______ alleles
Dominant, Recessive
___ copies of a recessive allele must be present for a person to have the disorder
2
A person who is ______ for a recessive disorder, does not have the disease but is a carrier
Heterozygous
A person who does not show disease symptoms, but can pass on the disease-causing allele to offspring
Carrier
_______ genetic disorders are far less common, but have greater chance of inheritance
Dominant
Genes that are located on the sex chromosomes
Sex-linked genes
Female genotype, male genotype
XX, XY
Females can only pass on an x chromosome to offspring, but males can pass on an ___ or a ___, which determines the sex of the offspring
X,Y
In the expression of sex-linked genes, a disease can be x-linked or y-linked, and dominant or recessive
Got it!
In the expression of sex-linked genes, because males only have one copy of each sex chromosome, they express all of the alleles on both chromosomes (but if they donate a disease carrying Y chromosome to offspring, and the disease is X-linked, the offspring won’t have the disease)
Got it!
Traits that are specifically on the sex chromosomes
Sex-linked traits
In a sex-linked disease that is X-linked, males are more likely to inherit the disease because, __________
they only have one x chromosome
A process that occurs in female sex cells, early in development, in which one x chromosome is randomly “turned off”
X chromosome-inactivation
Why does X chromosome-inactivation occur?
If both x chromosomes continued to produce proteins normally, development of the embryo would be impaired; humans have evolved to develop with the aid of only one x chromosome
Offspring which express a heterozygous phenotype that is somewhere between the two homozygous phenotypes of the parents; “mix”
Incomplete Dominance
Both traits are fully and separately express- neither allele is dominant nor recessive
Codominance
Traits produced by two or more genes
Polygenic Traits
A gene that can interfere, or overpower, the expression of other genes, regardless of which other genes an organism has inerited
Epistatic Gene
Phenotype is usually a mixture of genes AND _____
Environment
What does Mendel’s Law of Independent assortment state?
During gamete formation, gametes inherit alleles randomly; No Pattern
When is the Law of Independent Assortment NOT true?
With linked genes
Traits that appear to be inherited together frequently
Linked Traits
Where are linked traits/genes always found?
On the SAME chromosome
The ______ two genes are on a chromosome, the more likely they will be inherited together in gametes
Closer
The ______ two gametes are on a chromosome, the more likely they will be separated during meiosis
Farther
What accounts for linked genes not being inherited together in the same gametes?
Homologous chromosomes Cross Over
Maps of the relative locations of genes on a chromosome
Linkage Maps
The likelihood of genes being separated during meiosis/gamete formation, resulting in allele recombination
Recombination Frequency
The ______ genes are on a chromosome, the higher recombination frequency they have
Farther
How is recombination frequency found?
Crossing organisms with defined, linked traits:
The % of times the phenotypes of the linked traits are NOT found together in the offspring is the recombination frequency
On a linkage map, 1% recombination frequency is represented by ___ unit
1
Only ______ can carry sex-linked genetic disorders
Females; males can’t carry sex-linked genetic disorders because they only have one x, and if that x is affected, then they just have the disorder
Both males and females can be carriers of a(n) ________ disorder
Autosomal
Autosomal disorders are represented with _________, while sex-linked disorders are represented with _________
One letter (Dominant, Recessive); T t
Xs and Ys with exponents, dominant or recessive letters can represent the disease causing allele, depending on the disease
A chart that can help trace the phenotypes and genotypes in a family to determine whether people carry recessive alleles
Pedigree
In a pedigree, if roughly the same number of males and females have the disorder, it is likely ______
If more males have the disorder, it is likely _______
Autosomal, Sex-Linked
A picture of all of the chromosomes in a cell
Karyotype
How can Karyotypes be used to find chromosomal disorders?
Karyotypes show changes in chromosomes, by revealing their patterns/bands with a stain
What did Morgan’s research with crossovers indicate to Mendel’s Law of Independent Assortment?
Chromosomes, not genes, assort independently
