Chapter 9: Genetics and Inheritance Flashcards
What do all living organisms inherit from their parents?
Genetic information (chromosomes)
How are genes arranged on chromosomes?
In a linear sequence.
What process allows new combinations of alleles to form?
Meiosis.
What happens during the fusion of gametes?
New allele combinations form.
What is a heritable factor that influences a characteristic?
A gene.
Where is a gene for a specific trait located?
At a locus on a chromosome.
What are variations of a gene called?
Alleles.
How do alleles differ from one another?
By one or a few bases.
What type of reproduction involves two parents?
Sexual reproduction.
How do asexual and sexual reproduction differ in chromosomes?
Asexual reproduction involves one chromosome; sexual involves pairs of chromosomes.
What are plasmids
and where are they found?
What are homologous chromosomes?
Chromosomes that carry the same genes.
What is the shape and size of homologous chromosomes?
Similar.
What happens when chromatids separate?
They become identical chromosomes.
What is a karyogram?
A chromosome representation based on size and shape.
What do diploid cells contain?
Pairs of homologous chromosomes.
What is the diploid number in humans?
46
What type of cells are haploid in humans?
Gametes.
What does the variable n represent?
The haploid number.
What results from the fusion of haploid gametes?
A diploid zygote.
Which nuclear division results in genetically identical cells?
Mitosis.
What does meiosis introduce into gametes?
Genetic variation.
How many chromosomes does the 23rd pair determine?
Sex.
What is the chromosomal difference between males and females?
XX = female
How many autosomes do humans have?
22 pairs.
What are the two divisions of meiosis?
Meiosis I and Meiosis II.
What is meiosis I known as?
Reduction division.
What happens during Prophase I of meiosis?
Crossing over of homologous chromosomes.
What occurs during Metaphase I in meiosis?
Random orientation of chromosomes.
Why can’t triploid cells undergo meiosis?
Homologous chromosomes cannot pair.
Where does meiosis occur in animals?
Gonads.
What is oogenesis?
Formation of female gametes.
What is spermatogenesis?
Formation of male gametes.
What is genotype?
Symbolic representation of alleles.
What is phenotype?
Observable characteristics or traits.
What does homozygous mean?
Two identical alleles.
What does heterozygous mean?
Two different alleles.
What is a dominant allele?
An allele expressed in both homozygous and heterozygous states.
What is a recessive allele?
An allele expressed only in the homozygous state.
What are co-dominant alleles?
Alleles that both affect the phenotype in a heterozygote.
What is a carrier in genetics?
An individual with a recessive allele not expressed in the phenotype.
What is a test cross?
Crossing a heterozygote with a homozygous recessive to determine genotype.
What does a Punnett grid show?
How parental alleles segregate and combine in offspring.
What is a monohybrid cross?
A cross showing inheritance of one trait.
What determines the phenotype in albinism?
The presence of the aa genotype.
What is the phenotype of Aa in albinism?
Pigmentation; carrier of albinism allele.
What ratio of tall to short plants was observed in Mendel’s F2 generation?
3:1.
What is co-dominance in snapdragons?
Red and white alleles both influence flower color.
How many alleles control ABO blood groups?
Three: IA
Which allele combination results in type O blood?
ii.
What is an example of an autosomal recessive disease?
Cystic fibrosis.
Which chromosomes determine sex-linked traits?
X and Y chromosomes.
Why are males more likely to exhibit X-linked traits?
Males have only one X chromosome.
What are examples of sex-linked traits?
Color blindness
What does Huntington’s disease result from?
A dominant allele.
What is a dihybrid cross?
A cross showing inheritance of two traits.
What is the phenotype ratio in a dihybrid cross of heterozygotes?
9:3:3:1.
What are linked genes?
Genes on the same chromosome that do not assort independently.
What creates recombinants in linked genes?
Crossing over.
What does the crossover value measure?
The distance between loci on a chromosome.
What is polygenic inheritance?
Traits controlled by multiple genes.
What is continuous variation?
A range of phenotypes from multiple genes and environmental factors.
What are examples of polygenic traits?
Height
What happens during meiosis II?
Separation of sister chromatids.
What is the diploid number in fruit flies?
8
What structure contains genes?
Chromosomes.
What are autosomal chromosomes?
Chromosomes not involved in determining sex.
What increases genetic variation during meiosis?
Crossing over and independent assortment.
What does a locus represent?
A gene’s specific position on a chromosome.
What happens to homologous chromosomes in meiosis I?
They pair and separate.
What are sister chromatids?
Identical copies of a chromosome after replication.
What is the result of random chromosome orientation?
Unique combinations of gametes.
Why is meiosis called reduction division?
It reduces the chromosome number by half.
What is the role of centromeres?
They attach chromatids in a chromosome.
How many alleles does each gamete carry per gene?
One.
What does a genotype describe?
The genetic composition of an organism.
What is the phenotype ratio in a monohybrid cross of heterozygotes?
3:1.
What happens during fertilization?
Two haploid cells combine to form a diploid zygote.
What is independent assortment?
Random distribution of homologous chromosomes during meiosis.
What is the phenotype of a heterozygous dominant genotype?
The dominant trait.
What does the symbol 2n represent?
Diploid chromosome number.
What increases the survival chances of offspring?
Genetic variation.
What is the smallest human chromosome?
Y chromosome.
How many genes are on the X chromosome?
Significantly more than the Y chromosome.
What happens during Prophase I?
Homologous chromosomes undergo crossing over.
What is the purpose of meiosis?
To produce gametes with half the chromosome number.
What is a phenotype influenced by?
Genotype and environment.
What results from a dihybrid test cross?
Four phenotype classes.
What are examples of recombinant phenotypes?
New combinations of parental traits.
What determines continuous variation?
Multiple genes and environmental influences.
What phenotype does IAIB produce?
AB blood type.
What does the ABO blood group demonstrate?
Multiple alleles and co-dominance.
What genetic structure replicates independently in prokaryotes?
Plasmids.
What does a karyogram display?
Chromosomes arranged by size and shape.
Question
Answer
What does the centromere connect?
Sister chromatids.
What genotype produces type AB blood?
IAIB.
What genotype produces type O blood?
ii.
What are homologous chromosomes?
Chromosomes with the same genes
What is the main purpose of mitosis?
Growth and repair.
What cells are formed by meiosis?
Gametes.
What is the diploid chromosome number in humans?
46
What type of allele is always expressed in the phenotype?
Dominant allele.
What is the role of meiosis in reproduction?
Halve chromosome numbers to form gametes.
What is the genotype of a homozygous dominant individual?
AA.
What is a dihybrid cross used to study?
Inheritance of two traits.
What is the result of random orientation?
Unique gametes.
What type of chromosome is the Y chromosome?
Sex chromosome.
What is the genetic makeup of a zygote?
Diploid.
What are examples of sex-linked traits?
Hemophilia
What happens during crossing over?
Chromatids exchange genetic material.
What genetic phenomenon explains tortoiseshell cats?
X-inactivation.
What ratio results from a heterozygous monohybrid cross?
3:1.
What type of inheritance is shown in height variation?
Polygenic inheritance.
What is the haploid number in humans?
23
What allele combination produces type A blood?
IAIA or IAi.
What allele combination produces type B blood?
IBIB or IBi.
What is a polygenic trait?
A trait controlled by multiple genes.
What is discrete variation?
Traits with limited categories.
What type of chromosomes are involved in autosomal linkage?
Non-sex chromosomes.
What are recombinant offspring?
Offspring with new combinations of traits.
What is the phenotype of Aa?
Dominant trait expressed.
What is the phenotype of aa?
Recessive trait expressed.
What happens during anaphase II?
Sister chromatids separate.
What is the function of spindle fibers?
To separate chromosomes.
What is a Punnett square used for?
Predicting offspring genotypes.
What is albinism caused by?
A recessive allele.
What is an example of a dominant genetic disorder?
Huntington’s disease.
What is the phenotype of IAi?
Type A blood.
What is a sex-linked trait?
A trait controlled by genes on sex chromosomes.
What are examples of polygenic traits?
Skin color
What type of inheritance explains ABO blood groups?
Multiple alleles and co-dominance.
What is a phenotype?
Observable traits.
What is a genotype?
Genetic composition of an organism.
What is a carrier?
An individual with a recessive allele not expressed in the phenotype.
What structure contains genetic material?
Chromosome.
What is the result of meiosis?
Four haploid cells.
What is the diploid number in humans?
46
What is the probability of a male child?
0.5
What is the function of crossing over?
To increase genetic variation.
What cells are haploid in humans?
Gametes.
What are plasmids?
Independent DNA in prokaryotes.
What is the phenotype of IBi?
Type B blood.
What is the genotype of a homozygous recessive individual?
aa.
What is the phenotype of a heterozygote?
Dominant trait.
What is nondisjunction?
Failure of chromosome separation.
What is independent assortment?
Random distribution of chromosomes during meiosis.
What ratio results from a dihybrid cross?
9:3:3:1.
What are autosomes?
Non-sex chromosomes.
What creates continuous variation?
Polygenic inheritance and environment.
What type of genetic condition is albinism?
Autosomal recessive.
What does mitosis produce?
Identical diploid cells.
What are homologous chromosomes?
Chromosomes with the same genes.
What are gametes?
Sex cells.
What is the function of meiosis?
Produce haploid cells.
What increases genetic diversity in gametes?
Crossing over and random orientation.
What determines sex in humans?
23rd chromosome pair.
What is the phenotype of ii?
Type O blood.
What increases the number of phenotypes?
Polygenic inheritance.
Question
Answer
- What is the role of meiosis in gamete formation?
To reduce chromosome number by half.
- What happens during metaphase I of meiosis?
Homologous chromosomes align in the center.
- How does crossing over contribute to variation?
By exchanging segments between homologous chromatids.
- What is a haploid cell?
A cell with one set of chromosomes.
- What is a diploid cell?
A cell with two sets of chromosomes.
- What determines whether an individual is male or female?
The 23rd chromosome pair (XX or XY).
What is the purpose of independent assortment?
To create genetic diversity in offspring.
How many chromosomes do human gametes have?
23
What is a phenotype ratio?
The ratio of observable traits in offspring.
What is the law of segregation?
Alleles separate into different gametes during meiosis.
What is a gamete?
A haploid sex cell.
What is fertilization?
The fusion of male and female gametes.
What happens during anaphase I of meiosis?
Homologous chromosomes are pulled apart.
What happens during prophase II of meiosis?
A new spindle apparatus forms in each haploid cell.
What is the result of meiosis II?
Four haploid cells.
What is a zygote?
A fertilized egg cell.
What type of inheritance pattern explains blood types?
Multiple alleles and co-dominance.
What does homozygous dominant mean?
Having two dominant alleles.
What does homozygous recessive mean?
Having two recessive alleles.
What does heterozygous mean?
Having one dominant and one recessive allele.
What is a test cross used for?
To determine if an individual is heterozygous or homozygous.
What is an autosomal recessive condition?
A genetic disorder caused by two recessive alleles.
What does polygenic inheritance affect?
Traits controlled by multiple genes.
How does the Y chromosome differ from the X chromosome?
It is smaller and contains fewer genes.
What is the phenotype of a homozygous recessive individual?
The recessive trait.
What is codominance?
Both alleles are fully expressed in a heterozygote.
What does random orientation lead to in meiosis?
Genetic diversity in gametes.
What is a locus?
The location of a gene on a chromosome.
What is the phenotype ratio in a heterozygous monohybrid cross?
3:1.
How does a heterozygous genotype express traits?
The dominant allele is expressed.
What is a dihybrid cross?
A genetic cross examining two traits.
What is continuous variation?
A range of phenotypes influenced by multiple genes.
What happens during telophase II of meiosis?
Four nuclei form
What are sister chromatids?
Identical copies of a replicated chromosome.
What does an autosome carry?
Genes unrelated to sex determination.
What type of cell division results in haploid cells?
Meiosis.
What does independent assortment ensure?
That gametes have unique combinations of alleles.
What is the genotype of a carrier?
Heterozygous (Aa).
What is the result of nondisjunction in meiosis?
Aneuploidy (abnormal chromosome number).
What is a recombinant chromosome?
A chromosome with new combinations of alleles due to crossing over.
How many chromosomes are in a human zygote?
46
What is the dominant phenotype?
The trait expressed in the presence of at least one dominant allele.
How do alleles segregate during meiosis?
Into separate gametes.
What is the genotype of a homozygous dominant individual?
AA.
What is the genotype of a heterozygous individual?
Aa.
How is genetic variation increased in sexual reproduction?
Through crossing over and independent assortment.
What is a genotype ratio?
The ratio of genetic combinations in offspring.
What is the phenotype of IAIB blood type?
AB blood type.
What is the phenotype ratio in a dihybrid cross of heterozygotes?
9:3:3:1.
What does the term “sex-linked” mean?
A gene located on a sex chromosome.
How does a recessive allele behave in heterozygotes?
It is masked by the dominant allele.
What is a characteristic of linked genes?
They are inherited together unless separated by crossing over.
How many genes control polygenic traits?
Two or more genes.
What is a gametophyte?
The haploid stage in a plant’s life cycle.
How does meiosis I differ from mitosis?
It involves homologous chromosome separation.
What is a recombinant phenotype?
A trait combination not seen in the parents.
How does crossing over affect linked genes?
It produces new allele combinations.
What is an example of discrete variation?
Blood groups.
What is the phenotype ratio in a test cross of heterozygotes?
1:1.
What is the function of the centromere?
To hold sister chromatids together.
What happens in metaphase II of meiosis?
Chromosomes align at the cell center.
What is genetic linkage?
When genes are located close together on the same chromosome.
What is an example of an autosomal dominant disorder?
Huntington’s disease.
How do homologous chromosomes differ?
They have the same genes but may have different alleles.
What are examples of continuous variation?
Height
What is the genotype for type O blood?
ii.
