Biology 2024

• genetic disorder


  any condition that has been passed down from the parents
• genetic mutations


  random change that happens in an organism's genetic material
• sex chromosomes


  pair of chromosomes that determine an organism's gender. They do not crossover during meiosis because they have different genes.
• autosomes


  all of the chromosomes that are not sex chromosomes. Both males and females have the same autosomes and the same autosomal gene.
• homologous chromosomes


  pairs of 2 matching chromosomes; same size and they have the same genes at the same locations but different alleles for those genes
• somatic cells


  any cell of a living organism other than the reproductive cells
• mitosis


  cell division that creates two identical daughter cells (includes 1 cell division and creates 2 diploid cells instead of 4). in charge of making all other body cells and for dividing a single zygote into trillions of cells
• meiosis


  cell division process that forms four haploid gametes (sperm and egg) from a single diploid cell
• gametes


  sperm and eggs (made during meiosis and only contain 1 set of chromosomes) that are haploid
• haploid 


  a cell with only a single set of chromosomes/gametes

  hap=one, ploid=sets of chromosomes
• diploid


  containing two complete sets of chromosomes, one from each parent.

  di=two, ploid=sets of chromosomes
• sister chromatids


  two identical copies of a single chromosome that are attached to each other at the centromeres.
• centromere


  holds sister chromatids
• prophase I


  first phase of meiosis I, II, and mitosis. Chromosomes condense into a compact form that is easy to move, centromeres move to opposite sides of cell and send out spindle fibers. The membrane breaks apart so the spindle fibers can attach to the chromosomes and guide their movement. Crossing over occurs between homologous chromosomes exchanging DNA.
• tetrad


  during prophase I, homologous chromosomes come together to form a structure called a tetrad. Each homologous chromosome is made up of 2 sister chromatids (tetrad contains 4 chromatids).
• centrosomes


  organelles that control the separation of the chromosome during meiosis I and II. They send out spindle fibers to guide chromosomes's movement.
• metaphase I


  Second phase of cell division. Chromosomes finish attaching to spindle fibers and line up at the metaphase plate to divide.
• anaphase I


  Third phase of cell division. During anaphase, the chromosomes separate and move to opposite sides of the cell. In meiosis I, homologous chromosomes separate. In meiosis II and mitosis, sister chromatids separate.
• telophase I


  Fourth phase of cell division. Chromosomes at the poles of the cell and nucleus reforms around the chromosomes (condensed). A cleavage furrow forms where the cell splits.
• cleavage furrow


  a plasma membrane sealing at the cell division site. The cleavage furrow begins as a shallow groove and eventually deepens to divide the cytoplasm.
• cytokinesis


  the cleavage furrow fully contracts, pinching apart one cell into 2 daughter cells. Completion of cell division.
• meiosis II


  cell division that separates sister chromatids from each other, resulting in haploid cells
• prophase II


  similar to prophase I, but without crossing over
• metaphase II


  the pairs of sister chromatids attach to the spindle and line up at the middle of the cell
• anaphase II


  separates the sister chromatids from each other
• telophase II (meiosis I and II results)


  chromosomes becomes uncondensed (they go back to their longer shape)
• fertilization


  the process in which two haploid gametes fuse to form a zygote
• zygote


  a diploid cell created by a sperm fertilizing an egg; fertilized ovum
• mutations (meiosis)


  when DNA is copied incorrectly which can change the genotype of the offspring in meiosis
• mutations (mitosis)


  when DNA is copied incorrectly which cannot change the genotype of the offspring in mitosis
• X-inactivation


  deactivation of one X chromosome in every cell, early in the life of a female organism. Only one X chromosome is active in each cell.
• Point mutations


  a single base pair is copied incorrectly during DNA replication in interphase. They can change genes from one allele to another.
• chromosomal rearrangement


  a mutation in which unequal amounts of DNA are exchanged during crossing over. One chromosome gets extra DNA while the other ends up with missing DNA. This could lead to one chromosome getting multiple alleles for a single gene.
• karyotype


  a picture of all chromosomes in an individual's cells. They show the physical structure of the chromosome so they can detect any large abnormalities.
• nondisjunction


  the failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division, usually resulting in an abnormal distribution of chromosomes in the daughter nuclei.
• homologous chromosomes


  same genes, different alleles
• non-homologous chromosomes


  different genes
• sister chromatids (structure)


  same genes and alleles held together at centromere
• autosomal linkage


  when there are two gene loci found on the same autosomal chromosome, so they are quite likely to be inherited together.
• autosomal recessive


  two unaffected parents could not have an affected offspring, parents must be heterozygous