bio Flashcards
(29 cards)
asexual reproduction
asexual reproduction involves only one parent and produces genetically identical offspring
sexual reproduction
sexual reproduction requires two parents, contributing genetic material to create offspring with unique genetic variations
Describe the role of meiosis and fertilization in sexually reproducing organisms.
meiosis is the cell division process that creates haploid gametes (like sperm and egg cells) with half the number of chromosomes, while fertilization is the fusion of these haploid gametes from two parents to restore the diploid chromosome number, resulting in a new individual with genetic diversity from both parents
Explain the importance of homologous chromosomes in meiosis.
they allow for the exchange of genetic material through a process called “crossing over,” which results in genetic diversity by creating new combinations of alleles in the gametes produced, ultimately contributing to variation within a species
Describe how the chromosome number is reduced from diploid to haploid through the stages of meiosis.
separation of homologous chromosomes in anaphase I, effectively halving the chromosome number in each daughter cell
Provide three important differences between mitosis and meiosis.
Number of daughter cells:
Mitosis produces two daughter cells, while meiosis produces four.
Genetic diversity:
Mitosis results in genetically identical daughter cells, while meiosis produces genetically diverse daughter cells due to crossing over.
Chromosome number:
Mitosis maintains the diploid chromosome number, while meiosis reduces the chromosome number to haploid.
Cell type:
Mitosis occurs in somatic cells (body cells), while meiosis occurs in germ cells (sex cells).
Explain the importance of random fertilization to increase genetic variation
When a sperm cell (containing a unique combination of chromosomes due to crossing over and independent assortment) randomly fertilizes an egg cell (also with unique chromosome combinations), the resulting zygote has a completely new genetic makeup, further maximizing genetic variation in the offspring.
Explain the importance of independent assortment to increase genetic variation.
During metaphase I of meiosis, homologous chromosomes line up randomly at the equator of the cell, leading to independent assortment where each chromosome from a pair is randomly distributed to different gametes, creating a vast array of possible chromosome combinations.
Explain the importance of crossing over to increase genetic variation.
During prophase I of meiosis, homologous chromosomes exchange genetic material through a process called crossing over, resulting in new combinations of alleles on each chromosome, further increasing genetic diversity within the gametes.
law of segregation
which states that during gamete formation, the two alleles for a trait separate from each other, meaning each offspring receives only one allele from each parent
Law of Independent Assortment
the inheritance of one trait is independent of the inheritance of another trait, as long as the genes for those traits are on different chromosomes and segregate independently during meiosis
Define the difference between an allele and a gene.
A gene is a section of DNA that codes for a specific trait, while an allele is a different version of that same gene
complete dominance
One allele is dominant over the other, and the dominant allele completely masks the expression of the recessive allele (e.g., AA or Aa results in the dominant phenotype).
Incomplete Dominance
Neither allele is completely dominant, leading to an intermediate phenotype in heterozygotes (e.g., red + white = pink flowers).
Codominance: Both alleles are expressed equally in the heterozygote, with both traits visible (e.g., AB blood type, where both A and B alleles are expressed).
multiple alleles
More than two alleles exist for a gene, although an individual can only have two (e.g., ABO blood group system with alleles A, B, and O).
Pleiotropy: A single gene affects multiple traits or phenotypic characteristics (e.g., Marfan syndrome, affecting the skeleton, eyes, and heart).
Epistasis
One gene can mask the expression of another gene (e.g., ee genotype for coat color in dogs can mask any coat color genes).
Polygenic
A trait is influenced by multiple genes, each contributing to the phenotype (e.g., human skin color, height).
Phenotypic Plasticity
The ability of an organism to change its phenotype in response to environmental conditions (e.g., flowers that change color based on soil pH).
Understand the unique pattern of inheritance in sex-linked genes.
Sex-linked genes are located on the X or Y chromosomes. X-linked traits are more commonly expressed in males (XY), as they only have one X chromosome. Y-linked traits are passed from father to son. Males with a single recessive X-linked allele will express the trait, while females need two copies.
gene links
Two genes are linked if they are located close to each other on the same chromosome, reducing the chance of being separated during crossing over in meiosis.
how to map gene distances by using recombinant frequency.
This value is used to calculate the genetic distance between the genes in map units (centimorgans, cM).
A 1% recombinant frequency equals 1 cM, indicating the genes are 1 unit apart. The higher the recombinant frequency, the further apart the genes are.
Recombinant frequency is the percentage of offspring that have a different combination of alleles from the parents due to crossing over during meiosis
Aneuploidy
Abnormal chromosome number (too many or too few), caused by nondisjunction during meiosis (e.g., Down syndrome).
Polyploidy
Having more than two complete sets of chromosomes, common in plants.
nondisjunction
failure of chromosomes to separate properly during cell division
