Where new gene combinations come from
Grade 9 Science Worksheet - Challenge Me
Circle the best answer.
A gamete gets 1 chromosome from each pair. No crossing over happens. Ari deals the chromosome cards of a parent cell. Pair 1 carries genes A and B, and pair 2 carries gene C. With no crossing over, which gamete could not be made?
- a b C, since a light pair 1 chromosome cannot go with the dark pair 2 chromosome
- a b c, since a gamete cannot get three light alleles
- A B c, since a dark pair 1 chromosome cannot go with the light pair 2 chromosome
- A b C, since A and b sit on different chromosomes of pair 1
Chromosome cards (model, not to scale). Crossing over between D and E happens in some cells but not in others. Bo deals a parent cell with D and E on pair 1 and F on pair 2. Crossing over between D and E happens in some cells. How many gamete types are possible?
- 6 gamete types
- 4 gamete types
- 16 gamete types
- 8 gamete types
Read this first
Use this
Chromosome cards (model, not to scale). Parent 1 cell has 2 sets of chromosomes and 2 pairs. Pair 1: a dark chromosome with allele K and a light chromosome with allele k. Pair 2: a dark chromosome with allele M and a light chromosome with allele m. Each pair lines up on its own. Grid: the side edge for parent 2 is already dealt: K m, k m. The top edge for parent 1 is ?.
Esme deals pair cards to the edge of a grid. Genes K and M are on different pairs of parent 1. Which choice lists parent 1's gamete types for the top edge?
- K M, k m
- K k, M m
- K M, K m, k M, k m
- K M, K m, k m
Model test cross counts (model data)
group offspring parental types 880 recombinant types 120 total 1,000 Kira counts a model test cross: 880 offspring look like a parent, and 120 show a new combination. What is the recombination frequency?
- 12 percent
- 13.6 percent
- 50 percent
- 88 percent
Recombination frequencies for genes P, Q and R on one chromosome (model data)
gene pair frequency P and Q 4 percent Q and R 9 percent P and R 13 percent Luz reads recombination frequencies for genes P, Q and R on one chromosome. Map distances add up. Which gene lies in the middle?
- R, since P and R have the largest value, 13 percent
- No gene can be found, since percentages do not add
- P, since P and Q have the smallest value, 4 percent
- Q, since 4 + 9 = 13 matches the P to R distance
Notebook on crossing over
line what the notebook says 1 Before meiosis, each chromosome is copied into 2 sister chromatids 2 In prophase I, homologous chromosomes pair up gene for gene 3 Crossing over swaps pieces in prophase I and again in prophase II 4 The swaps make recombinant chromatids with new allele combinations Milo's notebook is about crossing over. One line is wrong. Which fix is right?
- Line 2 should say sister chromatids pair up and swap pieces with each other
- Line 3 should say crossing over happens in prophase I, not prophase II
- Line 1 should say the chromosomes are copied again before meiosis II
- Line 4 should say the swaps make brand-new alleles in each chromatid
Notebook on a cell with 8 pairs
line what the notebook says 1 Each pair can face either pole at the middle, in 2 ways 2 The pairs line up independently, so the choices multiply 3 With 8 pairs there are 2 × 8 = 16 line-ups 4 Crossing over adds more variety on top of this Noah's notebook is about a cell with 8 pairs of chromosomes. One line is wrong. Which fix is right?
- Line 4 should say crossing over adds new alleles on top of this
- Line 3 should multiply 2 eight times: 2⁸ = 256
- Line 2 should say the choices add up, one 2 for each of the 8 pairs
- Line 1 should say each pair has 1 way, with the dark chromosomes on one side
Notebook on a pair of chromosomes
line what the notebook says 1 Each chromosome was copied before meiosis, so it has 2 sister chromatids 2 In prophase I, the dark and light chromosomes of a pair lie side by side 3 The 2 sister chromatids of the dark chromosome swap pieces with each other 4 The swap happens in prophase I, before the pairs line up at the middle Pia's notebook is about a swap of pieces in a pair. One line is wrong. Which fix is right?
- Line 2 should say the dark and light chromosomes are identical copies
- Line 4 should say the swap happens in prophase II, after the cells divide
- Line 3 should say a dark chromatid swaps pieces with a light chromatid
- Line 1 should say the copying happens after the pairs line up at the middle
Claim card (model)
item value claim gametes made by different cells of one parent can differ even when no crossing over happens pairs in each parent cell 3 chromosomes in each pair a dark one and a light one Ren claims that gametes made by different cells of one parent can differ even when no crossing over happens. Which claim and reason are right?
- False, since the dark chromosomes travel to one gamete together and the light ones to another
- False, since crossing over is the one way that gametes from different cells can differ
- True, since each pair lines up at random, so gametes get different mixes of dark and light chromosomes
- True, since sister chromatids swap pieces before the pairs line up at the middle
Tala compares two groups. Group X makes offspring by budding, which gives copies. Group Y uses meiosis and fertilization. Which claim about variation for natural selection is right?
- Group Y offers more, since crossing over happens in both meiosis I and meiosis II
- The groups offer equal variation, since mutation is the source of variation in each group
- Group Y offers more, since crossing over makes new alleles that neither parent had
- Group Y offers more, since crossing over, assortment and fertilization make new allele combinations